diff --git a/docs-mini/README.introduction b/docs-mini/README.introduction
index e3ba7f9f9..8d8030f47 100644
--- a/docs-mini/README.introduction
+++ b/docs-mini/README.introduction
@@ -57,11 +57,15 @@ SGSubsystem and define at least a small set of functions:
         FGFX();
         virtual ~FGFX();
 
-        virtual void init();
-        virtual void reinit();
-        virtual void bind();
-        virtual void unbind();
-        virtual void update(double dt);
+        // Subsystem API.
+        void bind() override;
+        void init() override;
+        void reinit() override;
+        void unbind() override;
+        void update(double dt) override;
+
+        // Subsystem identification.
+        static const char* subsystemName() { return "fx"; }
     };
 
 The init() functions should make sure everything is set and ready so the
diff --git a/src/AIModel/AIManager.hxx b/src/AIModel/AIManager.hxx
index 96cff2bf9..ae292b598 100644
--- a/src/AIModel/AIManager.hxx
+++ b/src/AIModel/AIManager.hxx
@@ -41,14 +41,18 @@ public:
     FGAIManager();
     virtual ~FGAIManager();
 
+    // Subsystem API.
+    void bind() override;
     void init() override;
-    void shutdown() override;
     void postinit() override;
     void reinit() override;
-    void bind() override;
+    void shutdown() override;
     void unbind() override;
     void update(double dt) override;
 
+    // Subsystem identification.
+    static const char* subsystemName() { return "ai-model"; }
+
     void updateLOD(SGPropertyNode* node);
     void attach(FGAIBase *model);
 
@@ -89,8 +93,6 @@ public:
 
     double calcRangeFt(const SGVec3d& aCartPos, const FGAIBase* aObject) const;
 
-    static const char* subsystemName() { return "ai-model"; }
-
     /**
      * @brief Retrieve the representation of the user's aircraft in the AI manager
      * the position and velocity of this object are slaved to the user's aircraft,
diff --git a/src/AIModel/performancedb.hxx b/src/AIModel/performancedb.hxx
index e5bbcdf9a..9075eaa39 100644
--- a/src/AIModel/performancedb.hxx
+++ b/src/AIModel/performancedb.hxx
@@ -25,10 +25,13 @@ public:
     PerformanceDB();
     virtual ~PerformanceDB();
 
-    virtual void init();
-    virtual void shutdown();
+    // Subsystem API.
+    void init() override;
+    void shutdown() override;
+    void update(double dt) override;
 
-    virtual void update(double dt);
+    // Subsystem identification.
+    static const char* subsystemName() { return "aircraft-performance-db"; }
 
     bool havePerformanceDataForAircraftType(const std::string& acType) const;
 
@@ -40,8 +43,6 @@ public:
 
     PerformanceData* getDefaultPerformance() const;
 
-    static const char* subsystemName() { return "aircraft-performance-db"; }
-
 private:
     void load(const SGPath& path);
 
diff --git a/src/AIModel/submodel.hxx b/src/AIModel/submodel.hxx
index 0ce027c40..4557ffc7b 100644
--- a/src/AIModel/submodel.hxx
+++ b/src/AIModel/submodel.hxx
@@ -96,14 +96,15 @@ public:
     FGSubmodelMgr();
     ~FGSubmodelMgr() override;
 
-    void load();
-
+    // Subsystem API.
+    void bind() override;
     void init() override;
     void postinit() override;
-    void bind() override;
+    void shutdown() override;
     void unbind() override;
     void update(double dt) override;
-    void shutdown() override;
+
+    void load();
 
 private:
     typedef std::vector <submodel*> submodel_vector_type;
diff --git a/src/ATC/atc_mgr.hxx b/src/ATC/atc_mgr.hxx
index 9fa77ee63..fb1d50b5d 100644
--- a/src/ATC/atc_mgr.hxx
+++ b/src/ATC/atc_mgr.hxx
@@ -51,12 +51,14 @@ private:
 public:
     FGATCManager();
     ~FGATCManager();
+
+    // Subsystem API.
     void postinit() override;
     void shutdown() override;
+    void update(double time) override;
 
     void addController(FGATCController *controller);
     void removeController(FGATCController* controller);
-    void update(double time);
 };
 
 #endif // _ATC_MRG_HXX_
diff --git a/src/Aircraft/FlightHistory.hxx b/src/Aircraft/FlightHistory.hxx
index 5d6950b14..b791cf89d 100644
--- a/src/Aircraft/FlightHistory.hxx
+++ b/src/Aircraft/FlightHistory.hxx
@@ -57,10 +57,11 @@ public:
     FGFlightHistory();
     virtual ~FGFlightHistory();
 
-    virtual void init();
-    virtual void shutdown();
-    virtual void reinit();
-    virtual void update(double dt);
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void shutdown() override;
+    void update(double dt) override;
 
     PagedPathForHistory_ptr pagedPathForHistory(size_t max_entries, size_t newerThan = 0) const;
     /**
diff --git a/src/Aircraft/controls.hxx b/src/Aircraft/controls.hxx
index 970cc8c11..6c7cb35a4 100644
--- a/src/Aircraft/controls.hxx
+++ b/src/Aircraft/controls.hxx
@@ -257,12 +257,15 @@ public:
     FGControls();
     ~FGControls();
 
-    // Implementation of SGSubsystem.
-    void init ();
-    void bind ();
-    void unbind ();
-    void update (double dt);
-    virtual void reinit();
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "controls"; }
 
     // Reset function
     void reset_all(void);
@@ -636,8 +639,6 @@ public:
     // controls/autoflight/autopilot[n]/
     void set_autopilot_engage( int ap, bool val );
 
-    static const char* subsystemName() { return "controls"; }
-
 private:
     inline void do_autocoordination() {
         // check for autocoordination
diff --git a/src/Aircraft/replay.hxx b/src/Aircraft/replay.hxx
index de8f7be0c..3f559740f 100644
--- a/src/Aircraft/replay.hxx
+++ b/src/Aircraft/replay.hxx
@@ -65,17 +65,21 @@ public:
     FGReplay ();
     virtual ~FGReplay();
 
-    virtual void init();
-    virtual void reinit();
-    virtual void bind();
-    virtual void unbind();
-    virtual void update( double dt );
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "replay"; }
+
     bool start(bool NewTape=false);
 
     bool saveTape(const SGPropertyNode* ConfigData);
     bool loadTape(const SGPropertyNode* ConfigData);
 
-    static const char* subsystemName() { return "replay"; }
 private:
     void clear();
     FGReplayData* record(double time);
diff --git a/src/Airports/airportdynamicsmanager.hxx b/src/Airports/airportdynamicsmanager.hxx
index 691325444..195c34fc2 100644
--- a/src/Airports/airportdynamicsmanager.hxx
+++ b/src/Airports/airportdynamicsmanager.hxx
@@ -38,10 +38,14 @@ public:
     AirportDynamicsManager();
     virtual ~AirportDynamicsManager();
 
-    virtual void init();
-    virtual void shutdown();
-    virtual void update (double dt);
-    virtual void reinit();
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void shutdown() override;
+    void update(double dt) override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "airport-dynamics"; }
 
     static FGAirportDynamicsRef find(const std::string& icao);
 
@@ -49,8 +53,6 @@ public:
 
     FGAirportDynamicsRef dynamicsForICAO(const std::string& icao);
 
-    static const char* subsystemName() { return "airport-dynamics"; }
-
 private:
     typedef std::map<std::string, FGAirportDynamicsRef> ICAODynamicsDict;
     ICAODynamicsDict m_dynamics;
diff --git a/src/Autopilot/autopilot.hxx b/src/Autopilot/autopilot.hxx
index 3962081a8..fa6bf0945 100644
--- a/src/Autopilot/autopilot.hxx
+++ b/src/Autopilot/autopilot.hxx
@@ -40,9 +40,10 @@ public:
     Autopilot( SGPropertyNode_ptr rootNode, SGPropertyNode_ptr configNode = NULL );
     ~Autopilot();
 
-    void bind();
-    void unbind();
-    void update( double dt );
+    // Subsystem API.
+    void bind() override;
+    void unbind() override;
+    void update(double dt) override;
 
     void set_serviceable( bool value ) { _serviceable = value; }
     bool is_serviceable() const { return _serviceable; }
diff --git a/src/Autopilot/autopilotgroup.cxx b/src/Autopilot/autopilotgroup.cxx
index 0176f4598..b41ee4377 100644
--- a/src/Autopilot/autopilotgroup.cxx
+++ b/src/Autopilot/autopilotgroup.cxx
@@ -48,13 +48,15 @@ public:
         _nodeName(nodeName)
     {}
 
+    // Subsystem API.
+    void init() override;
+    InitStatus incrementalInit() override;
+    void reinit() override;
+
     virtual void addAutopilot( const std::string& name,
                                SGPropertyNode_ptr apNode,
                                SGPropertyNode_ptr config );
     virtual void removeAutopilot( const std::string & name );
-    void init();
-    InitStatus incrementalInit();
-    void reinit();
 
 private:
     void initFrom( SGPropertyNode_ptr rootNode, const char * childName );
diff --git a/src/Autopilot/component.hxx b/src/Autopilot/component.hxx
index 4afdb4658..8dfbadb57 100644
--- a/src/Autopilot/component.hxx
+++ b/src/Autopilot/component.hxx
@@ -48,11 +48,6 @@ protected:
                             const std::string& cfg_name,
                             SGPropertyNode& prop_root );
 
-   /**
-    * @brief the implementation of the update() method of the SGSubsystem
-    */
-    virtual void update( double dt );
-
    /**
     * @brief pure virtual function to be implemented by the derived classes. Gets called from
     * the update method if it's not disabled with the firstTime parameter set to true if this
@@ -93,6 +88,9 @@ public:
      */
     virtual ~Component();
 
+    // Subsystem API.
+    void update(double dt) override;
+
     /**
      * @brief configure this component from a property node. Iterates through
      *        all nodes found as children under configNode and calls configure
diff --git a/src/Autopilot/route_mgr.hxx b/src/Autopilot/route_mgr.hxx
index 59840f515..2f2ecd6f7 100644
--- a/src/Autopilot/route_mgr.hxx
+++ b/src/Autopilot/route_mgr.hxx
@@ -45,11 +45,15 @@ public:
     FGRouteMgr();
     ~FGRouteMgr();
 
-    void init ();
-    void postinit ();
-    void bind ();
-    void unbind ();
-    void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void postinit() override;
+    void unbind() override;
+    void update(double dt) override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "route-manager"; }
 
     bool isRouteActive() const;
 
@@ -100,8 +104,6 @@ public:
 
     flightgear::WayptRef waypointFromString(const std::string& target);
 
-    static const char* subsystemName() { return "route-manager"; }
-
 private:
     bool commandDefineUserWaypoint(const SGPropertyNode * arg, SGPropertyNode * root);
     bool commandDeleteUserWaypoint(const SGPropertyNode * arg, SGPropertyNode * root);
diff --git a/src/Canvas/canvas_mgr.hxx b/src/Canvas/canvas_mgr.hxx
index a82e1be25..4cc92c11f 100644
--- a/src/Canvas/canvas_mgr.hxx
+++ b/src/Canvas/canvas_mgr.hxx
@@ -27,8 +27,12 @@ class CanvasMgr : public simgear::canvas::CanvasMgr
 public:
     CanvasMgr();
 
-    virtual void init();
-    virtual void shutdown();
+    // Subsystem API.
+    void init() override;
+    void shutdown() override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "Canvas"; }
 
     /**
      * Get OpenGL texture name for given canvas
@@ -41,8 +45,6 @@ public:
      */
     unsigned int getCanvasTexId(const simgear::canvas::CanvasPtr& canvas) const;
 
-    static const char* subsystemName() { return "Canvas"; }
-
 protected:
 
     osg::observer_ptr<osg::Camera>      _gui_camera;
diff --git a/src/Canvas/gui_mgr.hxx b/src/Canvas/gui_mgr.hxx
index 5c78950af..68be7b5eb 100644
--- a/src/Canvas/gui_mgr.hxx
+++ b/src/Canvas/gui_mgr.hxx
@@ -39,13 +39,13 @@ class GUIMgr : public SGSubsystem
 public:
     GUIMgr();
 
+    // Subsystem API.
+    void init() override;
+    void shutdown() override;
+    void update(double dt) override;
+
     simgear::canvas::WindowPtr createWindow(const std::string& name = "");
 
-    virtual void init();
-    virtual void shutdown();
-
-    virtual void update(double dt);
-
     /**
      * Get simgear::canvas::Group containing all windows
      */
diff --git a/src/Cockpit/NavDisplay.hxx b/src/Cockpit/NavDisplay.hxx
index 6bf73e72c..c309e614d 100644
--- a/src/Cockpit/NavDisplay.hxx
+++ b/src/Cockpit/NavDisplay.hxx
@@ -62,8 +62,9 @@ public:
     NavDisplay(SGPropertyNode *node);
     virtual ~NavDisplay();
 
-    virtual void init();
-    virtual void update(double dt);
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 
     void invalidatePositionedCache()
     {
diff --git a/src/Cockpit/agradar.hxx b/src/Cockpit/agradar.hxx
index a95812a4c..184655a6b 100644
--- a/src/Cockpit/agradar.hxx
+++ b/src/Cockpit/agradar.hxx
@@ -37,8 +37,9 @@ public:
     agRadar ();
     virtual ~agRadar ();
 
-    virtual void init ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 
     void setUserPos();
     void setUserVec(double az, double el);
diff --git a/src/Cockpit/cockpitDisplayManager.hxx b/src/Cockpit/cockpitDisplayManager.hxx
index fe59b7007..4ac1419be 100644
--- a/src/Cockpit/cockpitDisplayManager.hxx
+++ b/src/Cockpit/cockpitDisplayManager.hxx
@@ -39,8 +39,9 @@ public:
     CockpitDisplayManager ();
     virtual ~CockpitDisplayManager ();
 
-    virtual void init();
-    virtual InitStatus incrementalInit();
+    // Subsystem API.
+    void init() override;
+    InitStatus incrementalInit() override;
 
 private:
     bool build (SGPropertyNode* config_props);
diff --git a/src/Cockpit/wxradar.hxx b/src/Cockpit/wxradar.hxx
index 086ecb51c..5a4fe7609 100644
--- a/src/Cockpit/wxradar.hxx
+++ b/src/Cockpit/wxradar.hxx
@@ -44,10 +44,11 @@ public:
     wxRadarBg();
     virtual ~wxRadarBg();
 
-    virtual void init();
-    virtual void shutdown();
+    // Subsystem API.
+    void init() override;
+    void shutdown() override;
+    void update(double dt) override;
 
-    virtual void update(double dt);
     virtual void valueChanged(SGPropertyNode *);
 
 protected:
diff --git a/src/Environment/environment_ctrl.cxx b/src/Environment/environment_ctrl.cxx
index 98f59cb9e..a50d569d0 100644
--- a/src/Environment/environment_ctrl.cxx
+++ b/src/Environment/environment_ctrl.cxx
@@ -106,12 +106,13 @@ class LayerInterpolateControllerImplementation : public LayerInterpolateControll
 public:
     LayerInterpolateControllerImplementation( SGPropertyNode_ptr rootNode );
     
-    virtual void init ();
-    virtual void reinit ();
-    virtual void postinit();
-    virtual void bind();
-    virtual void unbind();
-    virtual void update (double delta_time_sec);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void postinit() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double delta_time_sec) override;
 
 private:
     SGPropertyNode_ptr _rootNode;
diff --git a/src/Environment/environment_mgr.hxx b/src/Environment/environment_mgr.hxx
index 5948112a5..71dd1f649 100644
--- a/src/Environment/environment_mgr.hxx
+++ b/src/Environment/environment_mgr.hxx
@@ -46,12 +46,13 @@ public:
     FGEnvironmentMgr ();
     virtual ~FGEnvironmentMgr ();
 
-    virtual InitStatus incrementalInit ();
-    virtual void reinit ();
-    virtual void shutdown ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    InitStatus incrementalInit() override;
+    void reinit() override;
+    void shutdown() override;
+    void unbind() override;
+    void update(double dt) override;
 
     /**
      * Get the environment information for the plane's current position.
diff --git a/src/Environment/ephemeris.hxx b/src/Environment/ephemeris.hxx
index 0e51b0007..648ef199d 100644
--- a/src/Environment/ephemeris.hxx
+++ b/src/Environment/ephemeris.hxx
@@ -31,7 +31,7 @@ class SGEphemeris;
 class SGPropertyNode;
 
 /**
- * Wrap SGEphemeris in a susbsytem/property interface
+ * Wrap SGEphemeris in a subsystem/property interface
  */
 class Ephemeris : public SGSubsystem
 {
@@ -39,13 +39,15 @@ public:
     Ephemeris();
     ~Ephemeris();
 
-    virtual void bind();
-    virtual void unbind();
-    virtual void update(double dt);
-    virtual void init();
-    virtual void shutdown();
-    virtual void postinit();
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void postinit() override;
+    void shutdown() override;
+    void unbind() override;
+    void update(double dt) override;
 
+    // Subsystem identification.
     static const char* subsystemName() { return "ephemeris"; }
 
     SGEphemeris* data();
diff --git a/src/Environment/magvarmanager.hxx b/src/Environment/magvarmanager.hxx
index 202c00d97..73c4ac32a 100644
--- a/src/Environment/magvarmanager.hxx
+++ b/src/Environment/magvarmanager.hxx
@@ -34,11 +34,11 @@ public:
     FGMagVarManager();
     virtual ~FGMagVarManager();
 
-    virtual void init();
-    virtual void bind();
-    virtual void unbind();
-
-    virtual void update(double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     std::unique_ptr<SGMagVar> _magVar;
diff --git a/src/Environment/precipitation_mgr.hxx b/src/Environment/precipitation_mgr.hxx
index 360ee3ff5..c71f01ab3 100644
--- a/src/Environment/precipitation_mgr.hxx
+++ b/src/Environment/precipitation_mgr.hxx
@@ -45,11 +45,11 @@ public:
     FGPrecipitationMgr();
     virtual ~FGPrecipitationMgr();
 
-    // SGSubsystem methods
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void init ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void unbind() override;
+    void update(double dt) override;
 
     void setupSceneGraph(void);
     void setPrecipitationLevel(double l);
diff --git a/src/Environment/realwx_ctrl.cxx b/src/Environment/realwx_ctrl.cxx
index c1e0f44e6..c7066fd97 100644
--- a/src/Environment/realwx_ctrl.cxx
+++ b/src/Environment/realwx_ctrl.cxx
@@ -155,9 +155,13 @@ public:
     BasicRealWxController( SGPropertyNode_ptr rootNode, MetarRequester * metarRequester );
     virtual ~BasicRealWxController ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void shutdown ();
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void shutdown() override;
+    void unbind() override;
+    void update(double dt) override;
     
     /**
      * Create a metar-property binding at the specified property path,
@@ -173,10 +177,6 @@ public:
     MetarPropertiesList::iterator findMetarAtPath(const string &propPath);
 
 protected:
-    void bind();
-    void unbind();
-    void update( double dt );
-
     void checkNearbyMetar();
 
     long getMetarMaxAgeMin() const { return _max_age_n == NULL ? 0 : _max_age_n->getLongValue(); }
diff --git a/src/Environment/ridge_lift.hxx b/src/Environment/ridge_lift.hxx
index 26dc5e309..5518f1668 100644
--- a/src/Environment/ridge_lift.hxx
+++ b/src/Environment/ridge_lift.hxx
@@ -44,10 +44,11 @@ public:
     FGRidgeLift();
     ~FGRidgeLift();
 
-    virtual void bind();
-    virtual void unbind();
-    virtual void update(double dt);
-    virtual void init();
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void unbind() override;
+    void update(double dt) override;
 
     inline double getStrength() const { return strength; };
 
diff --git a/src/Environment/terrainsampler.cxx b/src/Environment/terrainsampler.cxx
index f298b25df..6179b0700 100644
--- a/src/Environment/terrainsampler.cxx
+++ b/src/Environment/terrainsampler.cxx
@@ -49,11 +49,13 @@ class AreaSampler : public SGSubsystem
 public:
     AreaSampler( SGPropertyNode_ptr rootNode );
     virtual ~AreaSampler();
-    void update( double dt );
-    void bind();
-    void unbind();
-    void init();
-    void reinit();
+
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
     int getElevationHistogramStep() const { return _elevationHistogramStep; }
     void setElevationHistograpStep( int value ) {
@@ -322,13 +324,14 @@ public:
     TerrainSamplerImplementation ( SGPropertyNode_ptr rootNode );
     virtual ~TerrainSamplerImplementation ();
 
-    virtual void init ();
-    virtual InitStatus incrementalInit ();
-    virtual void postinit();
-    virtual void reinit ();
-    virtual void bind();
-    virtual void unbind();
-    virtual void update (double delta_time_sec);
+    // Subsystem API.
+    void bind() override;
+    InitStatus incrementalInit() override;
+    void init() override;
+    void postinit() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double delta_time_sec) override;
 
 private:
     inline string areaSubsystemName( unsigned i ) {
diff --git a/src/FDM/ExternalNet/ExternalNet.hxx b/src/FDM/ExternalNet/ExternalNet.hxx
index c5f3cf83d..066443c85 100644
--- a/src/FDM/ExternalNet/ExternalNet.hxx
+++ b/src/FDM/ExternalNet/ExternalNet.hxx
@@ -54,11 +54,9 @@ public:
     // Destructor
     ~FGExternalNet();
 
-    // Reset flight params to a specific position
-    void init();
-
-    // update the fdm
-    void update( double dt );
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 };
 
 #endif // _EXTERNAL_NET_HXX
diff --git a/src/FDM/ExternalPipe/ExternalPipe.hxx b/src/FDM/ExternalPipe/ExternalPipe.hxx
index 934ed07f6..7ca5a2366 100644
--- a/src/FDM/ExternalPipe/ExternalPipe.hxx
+++ b/src/FDM/ExternalPipe/ExternalPipe.hxx
@@ -70,11 +70,9 @@ public:
     // Destructor
     ~FGExternalPipe();
 
-    // Reset flight params to a specific position
-    void init();
-
-    // update the fdm
-    void update( double dt );
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 };
 
 #endif // _EXTERNAL_PIPE_HXX
diff --git a/src/FDM/JSBSim/JSBSim.hxx b/src/FDM/JSBSim/JSBSim.hxx
index cb6ddb084..aac75222c 100644
--- a/src/FDM/JSBSim/JSBSim.hxx
+++ b/src/FDM/JSBSim/JSBSim.hxx
@@ -107,24 +107,19 @@ public:
     /// Destructor
     ~FGJSBsim();
 
+    // Subsystem API.
+    void init() override;
+    void resume() override;
+    void suspend() override;
+    void unbind() override;
+    void update(double dt) override;
+
     /// copy FDM state to LaRCsim structures
     bool copy_to_JSBsim();
 
     /// copy FDM state from LaRCsim structures
     bool copy_from_JSBsim();
 
-    /// Reset flight params to a specific position
-    void init();
-
-    /// Unbind properties
-    void unbind();
-
-    /// Suspend integration
-    void suspend();
-
-    /// Resume integration
-    void resume();
-
     /// @name Position Parameter Set
     //@{
     /** Set geocentric latitude
@@ -211,11 +206,6 @@ public:
     /// @name Position Parameter Update
     //@{
 
-
-    /** Update the position based on inputs, positions, velocities, etc.
-        @param dt delta time in seconds. */
-    void update(double dt);
-
     bool ToggleDataLogging(bool state);
     bool ToggleDataLogging(void);
 
diff --git a/src/FDM/LaRCsim/LaRCsim.hxx b/src/FDM/LaRCsim/LaRCsim.hxx
index b4708f860..01f2fe81c 100644
--- a/src/FDM/LaRCsim/LaRCsim.hxx
+++ b/src/FDM/LaRCsim/LaRCsim.hxx
@@ -48,18 +48,16 @@ public:
     FGLaRCsim( double dt );
     ~FGLaRCsim(void);
 
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
+
     // copy FDM state to LaRCsim structures
     bool copy_to_LaRCsim();
 
     // copy FDM state from LaRCsim structures
     bool copy_from_LaRCsim();
 
-    // reset flight params to a specific position
-    void init();
-
-    // update position based on inputs, positions, velocities, etc.
-    void update( double dt );
-
     // Positions
     void set_Latitude(double lat);  //geocentric
     void set_Longitude(double lon);
diff --git a/src/FDM/NullFDM.hxx b/src/FDM/NullFDM.hxx
index c966e2e7c..700cf5b2e 100644
--- a/src/FDM/NullFDM.hxx
+++ b/src/FDM/NullFDM.hxx
@@ -35,11 +35,9 @@ public:
     FGNullFDM( double dt );
     ~FGNullFDM();
 
-    // reset flight params to a specific position
-    void init();
-
-    // update position based on inputs, positions, velocities, etc.
-    void update( double dt );
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 };
 
 #endif // _NULLFDM_HXX
diff --git a/src/FDM/SP/ACMS.hxx b/src/FDM/SP/ACMS.hxx
index 23d43c178..566014324 100644
--- a/src/FDM/SP/ACMS.hxx
+++ b/src/FDM/SP/ACMS.hxx
@@ -34,11 +34,9 @@ public:
     FGACMS( double dt );
     ~FGACMS();
 
-    // reset flight params to a specific position
-    void init();
-
-    // update position based on properties
-    void update( double dt );
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 
 private:
     SGPropertyNode_ptr _alt, _speed, _climb_rate;
diff --git a/src/FDM/SP/ADA.hxx b/src/FDM/SP/ADA.hxx
index a87a1094f..061f607e1 100644
--- a/src/FDM/SP/ADA.hxx
+++ b/src/FDM/SP/ADA.hxx
@@ -73,11 +73,9 @@ public:
     FGADA( double dt );
     ~FGADA();
 
-    // reset flight params to a specific position
-    void init();
-
-    // update position based on inputs, positions, velocities, etc.
-    void update(double dt);
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 };
 
 #endif // _ADA_HXX
diff --git a/src/FDM/SP/AISim.hpp b/src/FDM/SP/AISim.hpp
index 168ea85b3..1636c53bf 100644
--- a/src/FDM/SP/AISim.hpp
+++ b/src/FDM/SP/AISim.hpp
@@ -75,11 +75,9 @@ public:
     FGAISim(double dt);
     ~FGAISim();
 
-    // reset flight params to a specific location
-    void init();
-
-    // update location based on properties
-    void update(double dt);
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 
     bool load(std::string path);
 
diff --git a/src/FDM/SP/Balloon.h b/src/FDM/SP/Balloon.h
index ecac4bd57..42a07caa5 100644
--- a/src/FDM/SP/Balloon.h
+++ b/src/FDM/SP/Balloon.h
@@ -63,17 +63,15 @@ public:
     FGBalloonSim( double dt );
     ~FGBalloonSim();
 
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
+
     // copy FDM state to BalloonSim structures
     bool copy_to_BalloonSim();
 
     // copy FDM state from BalloonSim structures
     bool copy_from_BalloonSim();
-
-    // reset flight params to a specific position
-    void init();
-
-    // update position based on inputs, positions, velocities, etc.
-    void update( double dt );
 };
 
 /****************************************************************************/
diff --git a/src/FDM/SP/MagicCarpet.hxx b/src/FDM/SP/MagicCarpet.hxx
index 5b09a57f6..92ea7d23d 100644
--- a/src/FDM/SP/MagicCarpet.hxx
+++ b/src/FDM/SP/MagicCarpet.hxx
@@ -34,11 +34,9 @@ public:
     FGMagicCarpet( double dt );
     ~FGMagicCarpet();
 
-    // reset flight params to a specific position
-    void init();
-
-    // update position based on inputs, positions, velocities, etc.
-    void update( double dt );
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 };
 
 #endif // _MAGICCARPET_HXX
diff --git a/src/FDM/UFO.hxx b/src/FDM/UFO.hxx
index dd9569eb8..d1e08d807 100644
--- a/src/FDM/UFO.hxx
+++ b/src/FDM/UFO.hxx
@@ -64,11 +64,9 @@ public:
     FGUFO( double dt );
     ~FGUFO();
 
-    // reset flight params to a specific position
-    void init();
-
-    // update position based on inputs, positions, velocities, etc.
-    void update( double dt );
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 };
 
 #endif // _UFO_HXX
diff --git a/src/FDM/YASim/YASim.hxx b/src/FDM/YASim/YASim.hxx
index a41aabbc9..2f23a1638 100644
--- a/src/FDM/YASim/YASim.hxx
+++ b/src/FDM/YASim/YASim.hxx
@@ -12,13 +12,11 @@ public:
     YASim(double dt);
     ~YASim();
 
-    // Load externally set stuff into the FDM
-    virtual void init();
-    virtual void bind();
-    virtual void reinit();
-
-    // Run an iteration
-    virtual void update(double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void update(double dt) override;
 
 private:
     void report();
diff --git a/src/FDM/fdm_shell.hxx b/src/FDM/fdm_shell.hxx
index 74d120296..8753f95de 100644
--- a/src/FDM/fdm_shell.hxx
+++ b/src/FDM/fdm_shell.hxx
@@ -44,20 +44,20 @@ public:
     FDMShell();
     ~FDMShell() override;
 
-    void init() override;
-    void shutdown() override;
-    void reinit() override;
-    void postinit() override;
-
+    // Subsystem API.
     void bind() override;
+    void init() override;
+    void postinit() override;
+    void reinit() override;
+    void shutdown() override;
     void unbind() override;
-
     void update(double dt) override;
 
-    FGInterface* getInterface() const;
-    
+    // Subsystem identification.
     static const char* subsystemName() { return "flight"; }
 
+    FGInterface* getInterface() const;
+
 private:
     void createImplementation();
 
diff --git a/src/FDM/flight.hxx b/src/FDM/flight.hxx
index 7f45207a0..83fb11f75 100644
--- a/src/FDM/flight.hxx
+++ b/src/FDM/flight.hxx
@@ -390,10 +390,12 @@ public:
     FGInterface( double dt );
     virtual ~FGInterface();
 
-    virtual void init ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update(double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void unbind() override;
+    void update(double dt) override;
+
     virtual bool ToggleDataLogging(bool state) { return false; }
     virtual bool ToggleDataLogging(void) { return false; }
 
diff --git a/src/GUI/new_gui.hxx b/src/GUI/new_gui.hxx
index d98db1407..d49102478 100644
--- a/src/GUI/new_gui.hxx
+++ b/src/GUI/new_gui.hxx
@@ -40,38 +40,16 @@ public:
      */
     virtual ~NewGUI ();
 
-    /**
-     * Initialize the GUI subsystem.
-     */
-    virtual void init ();
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void shutdown() override;
+    void unbind() override;
+    void update(double delta_time_sec) override;
 
-    virtual void shutdown ();
-
-    /**
-     * Reinitialize the GUI subsystem. Reloads all XML dialogs.
-     */
-    virtual void reinit ();
-
-    /**
-     * Bind properties for the GUI subsystem.
-     *
-     * Currently, this method binds the properties for showing and
-     * hiding the menu.
-     */
-    virtual void bind ();
-
-    /**
-     * Unbind properties for the GUI subsystem.
-     */
-    virtual void unbind ();
-
-    /**
-     * Update the GUI subsystem.
-     *
-     * Currently, this method is a no-op, because nothing the GUI
-     * subsystem does is time-dependent.
-     */
-    virtual void update (double delta_time_sec);
+    // Subsystem identification.
+    static const char* subsystemName() { return "gui"; }
 
     /**
      * Redraw the GUI picking up new GUI colors.
@@ -170,8 +148,6 @@ public:
 
     virtual puFont *getDefaultFont() { return _font; }
 
-    static const char* subsystemName() { return "gui"; }
-
 protected:
     /**
      * Test if the menubar is visible.
diff --git a/src/Input/FGEventInput.hxx b/src/Input/FGEventInput.hxx
index 05f3954e9..11c66150e 100644
--- a/src/Input/FGEventInput.hxx
+++ b/src/Input/FGEventInput.hxx
@@ -322,10 +322,12 @@ class FGEventInput : public SGSubsystem,
 public:
     FGEventInput();
     virtual ~FGEventInput();
+
+    // Subsystem API.
     void init() override;
     void postinit() override;
-    void update( double dt ) override;
     void shutdown() override;
+    void update(double dt) override;
 
     const static unsigned MAX_DEVICES = 1000;
     const static unsigned INVALID_DEVICE_INDEX = MAX_DEVICES + 1;
diff --git a/src/Input/FGHIDEventInput.hxx b/src/Input/FGHIDEventInput.hxx
index 764283629..4b1e05c45 100644
--- a/src/Input/FGHIDEventInput.hxx
+++ b/src/Input/FGHIDEventInput.hxx
@@ -39,12 +39,14 @@ public:
 
     virtual ~FGHIDEventInput();
 
-    void update(double dt) override;
+    // Subsystem API.
     void init() override;
+    void postinit() override;
     void reinit() override;
-    void postinit();
     void shutdown() override;
+    void update(double dt) override;
 
+    // Subsystem identification.
     static const char* subsystemName() { return "input-hid"; }
 
 private:
diff --git a/src/Input/FGJoystickInput.hxx b/src/Input/FGJoystickInput.hxx
index 862295a0b..aa1ce1090 100644
--- a/src/Input/FGJoystickInput.hxx
+++ b/src/Input/FGJoystickInput.hxx
@@ -43,10 +43,11 @@ public:
     FGJoystickInput();
     virtual ~FGJoystickInput();
 
-    virtual void init();
-    virtual void postinit();
-    virtual void reinit();
-    virtual void update( double dt );
+    // Subsystem API.
+    void init() override;
+    void postinit() override;
+    void reinit() override;
+    void update(double dt) override;
 
     static const int MAX_JOYSTICKS        = 16;
     static const int MAX_JOYSTICK_AXES    = _JS_MAX_AXES;
diff --git a/src/Input/FGKeyboardInput.hxx b/src/Input/FGKeyboardInput.hxx
index 35ba39277..fa93ab077 100644
--- a/src/Input/FGKeyboardInput.hxx
+++ b/src/Input/FGKeyboardInput.hxx
@@ -44,11 +44,12 @@ public:
     FGKeyboardInput();
     virtual ~FGKeyboardInput();
 
-    virtual void init();
-    virtual void postinit();
-    virtual void bind();
-    virtual void unbind();
-    virtual void update( double dt );
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void postinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
     static const int MAX_KEYS = 1024;
 
diff --git a/src/Input/FGLinuxEventInput.hxx b/src/Input/FGLinuxEventInput.hxx
index 49cf5a0c6..db6696ca4 100644
--- a/src/Input/FGLinuxEventInput.hxx
+++ b/src/Input/FGLinuxEventInput.hxx
@@ -70,8 +70,10 @@ class FGLinuxEventInput : public FGEventInput
 public:
     FGLinuxEventInput();
     virtual ~ FGLinuxEventInput();
-    virtual void update (double dt);
-    virtual void postinit();
+
+    // Subsystem API.
+    void postinit() override;
+    void update(double dt) override;
 
 protected:
 };
diff --git a/src/Input/FGMacOSXEventInput.hxx b/src/Input/FGMacOSXEventInput.hxx
index ff0d3287b..c6432e2d6 100644
--- a/src/Input/FGMacOSXEventInput.hxx
+++ b/src/Input/FGMacOSXEventInput.hxx
@@ -48,10 +48,12 @@ public:
     FGMacOSXEventInput();
 
     virtual ~FGMacOSXEventInput();
-    virtual void update(double dt);
-    virtual void init();
-    virtual void postinit();
-    virtual void shutdown();
+
+    // Subsystem API.
+    void init() override;
+    void postinit() override;
+    void shutdown() override;
+    void update(double dt) override;
 
 private:
     friend class FGMacOSXEventInputPrivate;
diff --git a/src/Input/FGMouseInput.hxx b/src/Input/FGMouseInput.hxx
index a6c3cee42..87f41b35d 100644
--- a/src/Input/FGMouseInput.hxx
+++ b/src/Input/FGMouseInput.hxx
@@ -45,11 +45,13 @@ public:
     FGMouseInput();
     virtual ~FGMouseInput() = default;
 
+    // Subsystem API.
     void init() override;
-    void shutdown() override;
     void reinit() override;
-    void update( double dt ) override;
+    void shutdown() override;
+    void update(double dt) override;
 
+    // Subsystem identification.
     static const char* subsystemName() { return "input-mouse"; }
 
     void doMouseClick (int b, int updown, int x, int y, bool mainWindow, const osgGA::GUIEventAdapter* ea);
diff --git a/src/Input/input.hxx b/src/Input/input.hxx
index e31ab9f4c..1fd9fbe6b 100644
--- a/src/Input/input.hxx
+++ b/src/Input/input.hxx
@@ -55,6 +55,7 @@ public:
      */
     virtual ~FGInput();
 
+    // Subsystem identification.
     static const char* subsystemName() { return "input"; }
 };
 
diff --git a/src/Instrumentation/HUD/HUD.hxx b/src/Instrumentation/HUD/HUD.hxx
index 29fefbc5d..81368587b 100644
--- a/src/Instrumentation/HUD/HUD.hxx
+++ b/src/Instrumentation/HUD/HUD.hxx
@@ -121,10 +121,11 @@ class HUD : public SGSubsystem,
 public:
     HUD();
     ~HUD();
-    void init();
-    void update(double);
 
-    void reinit();
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void update(double) override;
 
     // called from Main/renderer.cxx to draw 2D and 3D HUD
     void draw(osg::State&);
diff --git a/src/Instrumentation/KLN89/kln89.hxx b/src/Instrumentation/KLN89/kln89.hxx
index b55f91aeb..00468d5e4 100644
--- a/src/Instrumentation/KLN89/kln89.hxx
+++ b/src/Instrumentation/KLN89/kln89.hxx
@@ -96,10 +96,11 @@ public:
     KLN89(RenderArea2D* instrument);
     ~KLN89();
 
-    void bind();
-    void unbind();
-    void init();
-    void update(double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void unbind() override;
+    void update(double dt) override;
 
     // Set Units
     // m if true, ft if false
diff --git a/src/Instrumentation/adf.hxx b/src/Instrumentation/adf.hxx
index 6877d82d9..01ddb0775 100644
--- a/src/Instrumentation/adf.hxx
+++ b/src/Instrumentation/adf.hxx
@@ -43,8 +43,9 @@ public:
     ADF ( SGPropertyNode *node );
     virtual ~ADF ();
 
-    virtual void init ();
-    virtual void update (double delta_time_sec);
+    // Subsystem API.
+    void init() override;
+    void update(double delta_time_sec) override;
 
 private:
     void set_bearing (double delta_time_sec, double bearing);
diff --git a/src/Instrumentation/airspeed_indicator.hxx b/src/Instrumentation/airspeed_indicator.hxx
index 91aa26664..f8b0a135b 100644
--- a/src/Instrumentation/airspeed_indicator.hxx
+++ b/src/Instrumentation/airspeed_indicator.hxx
@@ -40,9 +40,10 @@ public:
     AirspeedIndicator ( SGPropertyNode *node );
     virtual ~AirspeedIndicator ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void update(double dt) override;
 
 private:
     void computeMach();
diff --git a/src/Instrumentation/altimeter.hxx b/src/Instrumentation/altimeter.hxx
index d8da96a6c..26278fda4 100644
--- a/src/Instrumentation/altimeter.hxx
+++ b/src/Instrumentation/altimeter.hxx
@@ -33,11 +33,12 @@ public:
     Altimeter (SGPropertyNode *node, const std::string& aDefaultName, double quantum = 0);
     virtual ~Altimeter ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void update (double dt);
-    virtual void bind();
-    virtual void unbind();
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
     double getSettingInHg() const;
     void setSettingInHg( double value );
diff --git a/src/Instrumentation/attitude_indicator.hxx b/src/Instrumentation/attitude_indicator.hxx
index f75cc6a07..0ca4a9e69 100644
--- a/src/Instrumentation/attitude_indicator.hxx
+++ b/src/Instrumentation/attitude_indicator.hxx
@@ -42,11 +42,12 @@ public:
     AttitudeIndicator ( SGPropertyNode *node );
     virtual ~AttitudeIndicator ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     std::string _name;
diff --git a/src/Instrumentation/clock.hxx b/src/Instrumentation/clock.hxx
index 88567ff00..2c986fecf 100644
--- a/src/Instrumentation/clock.hxx
+++ b/src/Instrumentation/clock.hxx
@@ -32,8 +32,9 @@ public:
     Clock(SGPropertyNode *node);
     virtual ~Clock();
 
-    virtual void init();
-    virtual void update(double dt);
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 
 private:
     std::string _name;
diff --git a/src/Instrumentation/commradio.cxx b/src/Instrumentation/commradio.cxx
index b7f2dd33c..56e3a959b 100644
--- a/src/Instrumentation/commradio.cxx
+++ b/src/Instrumentation/commradio.cxx
@@ -461,10 +461,11 @@ public:
     CommRadioImpl(SGPropertyNode_ptr node);
     virtual ~CommRadioImpl();
 
-    void update(double dt) override;
-    void init() override;
+    // Subsystem API.
     void bind() override;
+    void init() override;
     void unbind() override;
+    void update(double dt) override;
 
 private:
     bool _useEightPointThree = false;
diff --git a/src/Instrumentation/dclgps.hxx b/src/Instrumentation/dclgps.hxx
index f0c72873d..05795606b 100644
--- a/src/Instrumentation/dclgps.hxx
+++ b/src/Instrumentation/dclgps.hxx
@@ -202,12 +202,13 @@ public:
     DCLGPS(RenderArea2D* instrument);
     virtual ~DCLGPS() = 0;
 
-    virtual void draw(osg::State& state);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void unbind() override;
+    void update(double dt) override;
 
-    virtual void init();
-    virtual void bind();
-    virtual void unbind();
-    virtual void update(double dt);
+    virtual void draw(osg::State& state);
 
     // Expand a SIAP ident to the full procedure name.
     std::string ExpandSIAPIdent(const std::string& ident);
diff --git a/src/Instrumentation/dme.hxx b/src/Instrumentation/dme.hxx
index 252a8232a..5f6d76153 100644
--- a/src/Instrumentation/dme.hxx
+++ b/src/Instrumentation/dme.hxx
@@ -38,6 +38,7 @@ public:
     DME ( SGPropertyNode *node );
     virtual ~DME ();
 
+    // Subsystem API.
     void init() override;
     void reinit() override;
     void update(double delta_time_sec) override;
diff --git a/src/Instrumentation/gps.hxx b/src/Instrumentation/gps.hxx
index 2e174cb78..97b522531 100644
--- a/src/Instrumentation/gps.hxx
+++ b/src/Instrumentation/gps.hxx
@@ -64,13 +64,12 @@ public:
     GPS ();
     virtual ~GPS ();
 
-    // SGSubsystem interface
-    virtual void init ();
-    virtual void reinit ();
-    virtual void update (double delta_time_sec);
-
-    virtual void bind();
-    virtual void unbind();
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double delta_time_sec) override;
 
     // RNAV interface
     virtual SGGeod position();
diff --git a/src/Instrumentation/gsdi.hxx b/src/Instrumentation/gsdi.hxx
index fa769be41..15c1019b4 100644
--- a/src/Instrumentation/gsdi.hxx
+++ b/src/Instrumentation/gsdi.hxx
@@ -47,8 +47,9 @@ public:
     GSDI(SGPropertyNode *node);
     virtual ~GSDI();
 
-    virtual void init();
-    virtual void update(double dt);
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 
 private:
     std::string _name;
diff --git a/src/Instrumentation/heading_indicator.hxx b/src/Instrumentation/heading_indicator.hxx
index 2f5bfec6b..54d9bb55c 100644
--- a/src/Instrumentation/heading_indicator.hxx
+++ b/src/Instrumentation/heading_indicator.hxx
@@ -39,11 +39,12 @@ public:
     HeadingIndicator ();
     virtual ~HeadingIndicator ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     Gyro _gyro;
diff --git a/src/Instrumentation/heading_indicator_dg.hxx b/src/Instrumentation/heading_indicator_dg.hxx
index bbb9d13fc..1047d90a1 100644
--- a/src/Instrumentation/heading_indicator_dg.hxx
+++ b/src/Instrumentation/heading_indicator_dg.hxx
@@ -37,11 +37,12 @@ public:
     HeadingIndicatorDG ();
     virtual ~HeadingIndicatorDG ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     Gyro _gyro;
diff --git a/src/Instrumentation/heading_indicator_fg.hxx b/src/Instrumentation/heading_indicator_fg.hxx
index 62efe7bf6..a3dad5955 100644
--- a/src/Instrumentation/heading_indicator_fg.hxx
+++ b/src/Instrumentation/heading_indicator_fg.hxx
@@ -39,11 +39,12 @@ public:
     HeadingIndicatorFG ();
     virtual ~HeadingIndicatorFG ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     Gyro _gyro;
diff --git a/src/Instrumentation/inst_vertical_speed_indicator.hxx b/src/Instrumentation/inst_vertical_speed_indicator.hxx
index 2782550c4..2762f897e 100644
--- a/src/Instrumentation/inst_vertical_speed_indicator.hxx
+++ b/src/Instrumentation/inst_vertical_speed_indicator.hxx
@@ -54,9 +54,10 @@ public:
     InstVerticalSpeedIndicator ( SGPropertyNode *node );
     virtual ~InstVerticalSpeedIndicator ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void update(double dt) override;
 
 private:
     std::string _name;
diff --git a/src/Instrumentation/instrument_mgr.hxx b/src/Instrumentation/instrument_mgr.hxx
index dcd30d88f..ec42e43f9 100644
--- a/src/Instrumentation/instrument_mgr.hxx
+++ b/src/Instrumentation/instrument_mgr.hxx
@@ -31,8 +31,9 @@ public:
     FGInstrumentMgr ();
     virtual ~FGInstrumentMgr ();
 
-    virtual void init();
-    virtual InitStatus incrementalInit();
+    // Subsystem API.
+    void init() override;
+    InitStatus incrementalInit() override;
 
 private:
     bool build (SGPropertyNode* config_props);
diff --git a/src/Instrumentation/kr_87.hxx b/src/Instrumentation/kr_87.hxx
index 46ff924f1..2dee3d941 100644
--- a/src/Instrumentation/kr_87.hxx
+++ b/src/Instrumentation/kr_87.hxx
@@ -108,11 +108,12 @@ public:
     FGKR_87( SGPropertyNode *node );
     ~FGKR_87();
 
-    void init ();
-    void reinit ();
-    void bind ();
-    void unbind ();
-    void update (double dt_sec);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt_sec) override;
 
     // Update nav/adf radios based on current postition
     void search ();
diff --git a/src/Instrumentation/mag_compass.hxx b/src/Instrumentation/mag_compass.hxx
index 3e9106896..f5d06edc7 100644
--- a/src/Instrumentation/mag_compass.hxx
+++ b/src/Instrumentation/mag_compass.hxx
@@ -45,9 +45,10 @@ public:
     MagCompass ();
     virtual ~MagCompass ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void update(double dt) override;
 
 private:
     double _rate_degps;
diff --git a/src/Instrumentation/marker_beacon.hxx b/src/Instrumentation/marker_beacon.hxx
index 6b18c8e6f..d52d06b2e 100644
--- a/src/Instrumentation/marker_beacon.hxx
+++ b/src/Instrumentation/marker_beacon.hxx
@@ -66,11 +66,12 @@ public:
     FGMarkerBeacon(SGPropertyNode *node);
     ~FGMarkerBeacon();
 
-    void init () override;
-    void reinit () override;
-    void bind () override;
-    void unbind () override;
-    void update (double dt) override;
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
     void search ();
 
diff --git a/src/Instrumentation/mk_viii.hxx b/src/Instrumentation/mk_viii.hxx
index aeea823cb..35b7d9ada 100644
--- a/src/Instrumentation/mk_viii.hxx
+++ b/src/Instrumentation/mk_viii.hxx
@@ -1374,10 +1374,11 @@ class MK_VIII : public SGSubsystem
 public:
     MK_VIII (SGPropertyNode *node);
 
-    virtual void init ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void unbind() override;
+    void update(double dt) override;
 };
 
 #ifdef _MSC_VER
diff --git a/src/Instrumentation/mrg.hxx b/src/Instrumentation/mrg.hxx
index 9a3fc6e93..6e517a75f 100644
--- a/src/Instrumentation/mrg.hxx
+++ b/src/Instrumentation/mrg.hxx
@@ -40,11 +40,12 @@ public:
     MasterReferenceGyro ();
     virtual ~MasterReferenceGyro ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     static const double gravity; //conversion factor
diff --git a/src/Instrumentation/navradio.hxx b/src/Instrumentation/navradio.hxx
index cdaad8f12..bebbed7c0 100644
--- a/src/Instrumentation/navradio.hxx
+++ b/src/Instrumentation/navradio.hxx
@@ -173,9 +173,10 @@ public:
     FGNavRadio(SGPropertyNode *node);
     ~FGNavRadio();
 
-    void init ();
-    void reinit ();
-    void update (double dt);
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void update(double dt) override;
 
     // Update nav/adf radios based on current postition
     void search ();
diff --git a/src/Instrumentation/newnavradio.cxx b/src/Instrumentation/newnavradio.cxx
index 112ad887d..767878aee 100644
--- a/src/Instrumentation/newnavradio.cxx
+++ b/src/Instrumentation/newnavradio.cxx
@@ -808,8 +808,9 @@ public:
     NavRadioImpl( SGPropertyNode_ptr node );
     virtual ~NavRadioImpl();
 
-    virtual void update( double dt );
-    virtual void init();
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 
 private:
     void search();
diff --git a/src/Instrumentation/rad_alt.hxx b/src/Instrumentation/rad_alt.hxx
index 4e18f1506..754857af9 100644
--- a/src/Instrumentation/rad_alt.hxx
+++ b/src/Instrumentation/rad_alt.hxx
@@ -34,10 +34,11 @@ public:
     RadarAltimeter ( SGPropertyNode *node );
     virtual ~RadarAltimeter ();
 
-private:
-    virtual void init ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void init() override;
+    void update(double dt) override;
 
+private:
     void update_altitude();
     void updateSetHeight();
 
diff --git a/src/Instrumentation/slip_skid_ball.hxx b/src/Instrumentation/slip_skid_ball.hxx
index e0ad396b0..6d808dca5 100644
--- a/src/Instrumentation/slip_skid_ball.hxx
+++ b/src/Instrumentation/slip_skid_ball.hxx
@@ -34,9 +34,10 @@ public:
     SlipSkidBall ( SGPropertyNode *node );
     virtual ~SlipSkidBall ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void update(double dt) override;
 
 private:
     std::string _name;
diff --git a/src/Instrumentation/tacan.hxx b/src/Instrumentation/tacan.hxx
index 680d2bae9..4763d8449 100644
--- a/src/Instrumentation/tacan.hxx
+++ b/src/Instrumentation/tacan.hxx
@@ -38,9 +38,10 @@ public:
     TACAN(SGPropertyNode *node);
     virtual ~TACAN();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void update (double delta_time_sec);
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void update(double delta_time_sec) override;
 
 private:
     void disabled(bool force = false);
diff --git a/src/Instrumentation/tcas.hxx b/src/Instrumentation/tcas.hxx
index aaf1327bb..6d768862d 100644
--- a/src/Instrumentation/tcas.hxx
+++ b/src/Instrumentation/tcas.hxx
@@ -381,13 +381,13 @@ private:
 public:
     TCAS (SGPropertyNode* node);
 
-    virtual void bind   (void);
-    virtual void unbind (void);
-    virtual void init   (void);
-    virtual void reinit (void);
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
-	
     /* configuration options */
     int  _verticalRange;
     int  _lateralRange;
diff --git a/src/Instrumentation/transponder.hxx b/src/Instrumentation/transponder.hxx
index 317b5745d..4a81fb0aa 100644
--- a/src/Instrumentation/transponder.hxx
+++ b/src/Instrumentation/transponder.hxx
@@ -34,10 +34,11 @@ public:
     Transponder(SGPropertyNode *node);
     virtual ~Transponder();
 
-    void init () override;
-    void update (double dt) override;
+    // Subsystem API.
     void bind() override;
+    void init() override;
     void unbind() override;
+    void update(double dt) override;
 
 protected:
     bool isPowerSwitchOn() const override;
diff --git a/src/Instrumentation/turn_indicator.hxx b/src/Instrumentation/turn_indicator.hxx
index ac85243a3..15399e474 100644
--- a/src/Instrumentation/turn_indicator.hxx
+++ b/src/Instrumentation/turn_indicator.hxx
@@ -41,11 +41,12 @@ public:
     TurnIndicator ( SGPropertyNode *node );
     virtual ~TurnIndicator ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     Gyro _gyro;
diff --git a/src/Instrumentation/vertical_speed_indicator.hxx b/src/Instrumentation/vertical_speed_indicator.hxx
index 103806e0b..9387b2021 100644
--- a/src/Instrumentation/vertical_speed_indicator.hxx
+++ b/src/Instrumentation/vertical_speed_indicator.hxx
@@ -37,9 +37,10 @@ public:
     VerticalSpeedIndicator ( SGPropertyNode *node );
     virtual ~VerticalSpeedIndicator ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void update(double dt) override;
 
 private:
     double _casing_pressure_Pa = 0.0;
diff --git a/src/Main/fg_io.hxx b/src/Main/fg_io.hxx
index a45af25b9..61c957d18 100644
--- a/src/Main/fg_io.hxx
+++ b/src/Main/fg_io.hxx
@@ -40,13 +40,13 @@ public:
     FGIO();
     ~FGIO();
 
-    void init();
-    void reinit();
-    void bind();
-    void unbind();
-    void update( double dt );
-
-    void shutdown();
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void shutdown() override;
+    void unbind() override;
+    void update(double dt) override;
 
     /**
      * helper to determine early in startup, if MP will be used.
diff --git a/src/Main/fg_props.hxx b/src/Main/fg_props.hxx
index d0c6f367f..7b910485d 100644
--- a/src/Main/fg_props.hxx
+++ b/src/Main/fg_props.hxx
@@ -23,10 +23,11 @@ public:
     FGProperties ();
     virtual ~FGProperties ();
 
-    void init ();
-    void bind ();
-    void unbind ();
-    void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     simgear::TiedPropertyList _tiedProperties;
diff --git a/src/Main/logger.hxx b/src/Main/logger.hxx
index 51d59ac18..13498aae4 100644
--- a/src/Main/logger.hxx
+++ b/src/Main/logger.hxx
@@ -20,12 +20,12 @@
 class FGLogger : public SGSubsystem
 {
 public:
-    // Implementation of SGSubsystem
-    virtual void init ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     /**
diff --git a/src/Model/acmodel.hxx b/src/Model/acmodel.hxx
index 628953fca..66ed0b54c 100644
--- a/src/Model/acmodel.hxx
+++ b/src/Model/acmodel.hxx
@@ -24,17 +24,20 @@ public:
     FGAircraftModel ();
     virtual ~FGAircraftModel ();
 
-    virtual void init ();
-    virtual void shutdown ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void shutdown() override;
+    void unbind() override;
+    void update(double dt) override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "aircraft-model"; }
+
     virtual SGModelPlacement * get3DModel() { return _aircraft.get(); }
     virtual SGVec3d& getVelocity() { return _velocity; }
 
-    static const char* subsystemName() { return "aircraft-model"; }
-
 private:
     void deinit ();
 
diff --git a/src/Model/modelmgr.hxx b/src/Model/modelmgr.hxx
index 6fb2cb0cc..f3dbfd467 100644
--- a/src/Model/modelmgr.hxx
+++ b/src/Model/modelmgr.hxx
@@ -54,12 +54,15 @@ public:
     FGModelMgr ();
     virtual ~FGModelMgr ();
 
-    virtual void init ();
-    virtual void shutdown ();
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void shutdown() override;
+    void unbind() override;
+    void update(double dt) override;
 
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem identification.
+    static const char* subsystemName() { return "model-manager"; }
 
     virtual void add_model (SGPropertyNode * node);
 
@@ -83,8 +86,6 @@ public:
      */
     virtual void remove_instance (Instance * instance);
 
-    static const char* subsystemName() { return "model-manager"; }
-
 private:
     /**
      * Listener class that adds models at runtime.
diff --git a/src/MultiPlayer/multiplaymgr.hxx b/src/MultiPlayer/multiplaymgr.hxx
index e8fa8e72e..a0c004b13 100644
--- a/src/MultiPlayer/multiplaymgr.hxx
+++ b/src/MultiPlayer/multiplaymgr.hxx
@@ -54,11 +54,11 @@ public:
     FGMultiplayMgr();
     ~FGMultiplayMgr();
 
-    virtual void init(void);
-    virtual void update(double dt);
-
-    virtual void shutdown(void);
-    virtual void reinit();
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void shutdown() override;
+    void update(double dt) override;
 
     // transmitter
 
diff --git a/src/Network/DNSClient.hxx b/src/Network/DNSClient.hxx
index 2366e19e8..875783676 100644
--- a/src/Network/DNSClient.hxx
+++ b/src/Network/DNSClient.hxx
@@ -31,18 +31,20 @@ public:
     FGDNSClient();
     virtual ~FGDNSClient();
 
+    // Subsystem API.
+    void init() override;
+    void postinit() override;
+    void shutdown() override;
+    void update(double) override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "dns"; }
+
     void makeRequest(const simgear::DNS::Request_ptr& req);
 
 //    simgear::HTTP::Client* client() { return _http.get(); }
 //    simgear::HTTP::Client const* client() const { return _http.get(); }
 
-    virtual void init();
-    virtual void postinit();
-    virtual void shutdown();
-    virtual void update(double);
-
-    static const char* subsystemName() { return "dns"; }
-
 private:
     bool _inited;
     std::unique_ptr<simgear::DNS::Client> _dns;
diff --git a/src/Network/HTTPClient.hxx b/src/Network/HTTPClient.hxx
index 70de53934..2bb166c6a 100644
--- a/src/Network/HTTPClient.hxx
+++ b/src/Network/HTTPClient.hxx
@@ -31,16 +31,20 @@ public:
     FGHTTPClient();
     virtual ~FGHTTPClient();
 
+    // Subsystem API.
+    void init() override;
+    void postinit() override;
+    void shutdown() override;
+    void update(double) override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "http"; }
+
     void makeRequest(const simgear::HTTP::Request_ptr& req);
 
     simgear::HTTP::Client* client() { return _http.get(); }
     simgear::HTTP::Client const* client() const { return _http.get(); }
 
-    virtual void init();
-    virtual void postinit();
-    virtual void shutdown();
-    virtual void update(double);
-
     bool isDefaultCatalogInstalled() const;
     void addDefaultCatalog();
 
@@ -48,8 +52,6 @@ public:
     std::string getDefaultCatalogUrl() const;
     std::string getDefaultCatalogFallbackUrl() const;
 
-    static const char* subsystemName() { return "http"; }
-
 private:
     bool _inited;
     std::unique_ptr<simgear::HTTP::Client> _http;
diff --git a/src/Network/Swift/swift_connection.hxx b/src/Network/Swift/swift_connection.hxx
index 0220276a6..28f689446 100644
--- a/src/Network/Swift/swift_connection.hxx
+++ b/src/Network/Swift/swift_connection.hxx
@@ -38,20 +38,22 @@
 class SwiftConnection : public SGSubsystem
 {
 public:
-    bool startServer(const SGPropertyNode* arg, SGPropertyNode* root);
-    bool stopServer(const SGPropertyNode* arg, SGPropertyNode* root);
     SwiftConnection();
     ~SwiftConnection();
-    FGSwiftBus::CPlugin* plug;
 
-    virtual void         init(void);
-    virtual void         update(double delta_time_sec) override;
-    virtual void shutdown(void);
-    virtual void reinit();
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void shutdown() override;
+    void update(double delta_time_sec) override;
+
+    bool startServer(const SGPropertyNode* arg, SGPropertyNode* root);
+    bool stopServer(const SGPropertyNode* arg, SGPropertyNode* root);
+    FGSwiftBus::CPlugin* plug;
 
 private:
     bool serverRunning = false;
     bool initialized   = false;
 };
 
-#endif
\ No newline at end of file
+#endif
diff --git a/src/Network/fgcom.hxx b/src/Network/fgcom.hxx
index fcb115522..86e44fedd 100644
--- a/src/Network/fgcom.hxx
+++ b/src/Network/fgcom.hxx
@@ -30,13 +30,15 @@ public:
     FGCom();
     virtual ~FGCom();
 
-    virtual void bind();
-    virtual void unbind();
-    virtual void init();
-    virtual void postinit();
-    virtual void update(double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void postinit() override;
+    void shutdown() override;
+    void unbind() override;
+    void update(double dt) override;
+
     virtual void valueChanged(SGPropertyNode *prop);
-    virtual void shutdown();
     void iaxTextEvent(struct iaxc_ev_text text);
 
 private:
diff --git a/src/Network/http/httpd.cxx b/src/Network/http/httpd.cxx
index 661809b11..72e2bd4c9 100644
--- a/src/Network/http/httpd.cxx
+++ b/src/Network/http/httpd.cxx
@@ -179,31 +179,11 @@ public:
      */
     ~MongooseHttpd();
 
-    /**
-     * override SGSubsystem::init()
-     *
-     * Reads the configuration PropertyNode, installs URIHandlers and configures mongoose
-     */
-    void init();
-
-    /**
-     * override SGSubsystem::bind()
-     *
-     * Currently a noop
-     */
-    void bind();
-
-    /**
-     * override SGSubsystem::unbind()
-     * shutdown of mongoose, clear connections, unregister URIHandlers
-     */
-    void unbind();
-
-    /**
-     * overrride SGSubsystem::update()
-     * poll connections, check for changed properties
-     */
-    void update(double dt);
+    // Subsystem API.
+    void bind() override;            // Currently a noop
+    void init() override;            // Reads the configuration PropertyNode, installs URIHandlers and configures mongoose
+    void unbind() override;          // shutdown of mongoose, clear connections, unregister URIHandlers
+    void update(double dt) override; // poll connections, check for changed properties
 
     /**
      * Returns a URIHandler for the given uri
diff --git a/src/Scenery/scenery.hxx b/src/Scenery/scenery.hxx
index 28304bfa3..4262a4a54 100644
--- a/src/Scenery/scenery.hxx
+++ b/src/Scenery/scenery.hxx
@@ -71,13 +71,16 @@ public:
     FGScenery();
     ~FGScenery();
 
-    // Implementation of SGSubsystem.
-    void init ();
-    void reinit();
-    void shutdown ();
-    void bind ();
-    void unbind ();
-    void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void shutdown() override;
+    void unbind() override;
+    void update(double dt) override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "scenery"; }
 
     /// Compute the elevation of the scenery at geodetic latitude lat,
     /// geodetic longitude lon and not higher than max_alt.
@@ -141,9 +144,6 @@ public:
     // tile mgr api
     bool schedule_scenery(const SGGeod& position, double range_m, double duration=0.0);
     void materialLibChanged();
-    
-    static const char* subsystemName() { return "scenery"; }
-
 private:
     // the terrain engine
     FGTerrain* _terrain;
diff --git a/src/Scripting/NasalSys.hxx b/src/Scripting/NasalSys.hxx
index fd39faa4f..d6e316189 100644
--- a/src/Scripting/NasalSys.hxx
+++ b/src/Scripting/NasalSys.hxx
@@ -37,10 +37,15 @@ class FGNasalSys : public SGSubsystem
 public:
     FGNasalSys();
     virtual ~FGNasalSys();
+
+    // Subsystem API.
     void init() override;
     void shutdown() override;
     void update(double dt) override;
 
+    // Subsystem identification.
+    static const char* subsystemName() { return "nasal"; }
+
     // Loads a nasal script from an external file and inserts it as a
     // global module of the specified name.
     bool loadModule(SGPath file, const char* moduleName);
@@ -156,8 +161,6 @@ public:
     simgear::BufferedLogCallback* log() const
     { return _log.get(); }
 
-    static const char* subsystemName() { return "nasal"; }
-
 private:
     //friend class FGNasalScript;
     friend class FGNasalListener;
diff --git a/src/Sound/soundmanager.hxx b/src/Sound/soundmanager.hxx
index 9d6e6721e..607f77ef1 100644
--- a/src/Sound/soundmanager.hxx
+++ b/src/Sound/soundmanager.hxx
@@ -38,10 +38,14 @@ public:
     FGSoundManager();
     virtual ~FGSoundManager();
 
-    void init(void);
-    virtual void shutdown();
-    void update(double dt);
-    void reinit(void);
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void shutdown() override;
+    void update(double dt) override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "sound"; }
 
     void activate(bool State);
     void update_device_list();
@@ -73,8 +77,10 @@ public:
     FGSoundManager() { fgSetBool("/sim/sound/working", false);}
     ~FGSoundManager() {}
 
-    void update(double dt) {}
+    // Subsystem API.
+    void update(double dt) {} override
 
+    // Subsystem identification.
     static const char* subsystemName() { return "sound"; }
 };
 
diff --git a/src/Sound/voice.hxx b/src/Sound/voice.hxx
index b22651b61..bfaa96d46 100644
--- a/src/Sound/voice.hxx
+++ b/src/Sound/voice.hxx
@@ -55,9 +55,11 @@ class FGVoiceMgr : public SGSubsystem
 public:
     FGVoiceMgr();
     ~FGVoiceMgr();
-    void init(void);
-    void shutdown();
-    void update(double dt);
+
+    // Subsystem API.
+    void init() override;
+    void shutdown() override;
+    void update(double dt) override;
 
     class FGVoice;
 
diff --git a/src/Systems/electrical.hxx b/src/Systems/electrical.hxx
index 5eff6779b..1d7ebf63a 100644
--- a/src/Systems/electrical.hxx
+++ b/src/Systems/electrical.hxx
@@ -219,10 +219,11 @@ public:
     FGElectricalSystem ( SGPropertyNode *node );
     virtual ~FGElectricalSystem ();
 
-    void init () override;
-    void bind () override;
-    void unbind () override;
-    void update (double dt) override;
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void unbind() override;
+    void update(double dt) override;
 
     bool build (SGPropertyNode* config_props);
     float propagate( FGElectricalComponent *node, double dt,
diff --git a/src/Systems/pitot.hxx b/src/Systems/pitot.hxx
index 520a1d08a..4b2c55fe2 100644
--- a/src/Systems/pitot.hxx
+++ b/src/Systems/pitot.hxx
@@ -44,10 +44,11 @@ public:
     PitotSystem ( SGPropertyNode *node );
     virtual ~PitotSystem ();
 
-    virtual void init ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     std::string _name;
diff --git a/src/Systems/static.hxx b/src/Systems/static.hxx
index 41ea28aa8..f9551721e 100644
--- a/src/Systems/static.hxx
+++ b/src/Systems/static.hxx
@@ -40,11 +40,12 @@ public:
     StaticSystem ( int i );
     virtual ~StaticSystem ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     std::string _name;
diff --git a/src/Systems/system_mgr.hxx b/src/Systems/system_mgr.hxx
index f2ea8c0d4..8021e24b4 100644
--- a/src/Systems/system_mgr.hxx
+++ b/src/Systems/system_mgr.hxx
@@ -30,6 +30,7 @@ class FGSystemMgr : public SGSubsystemGroup
 public:
     FGSystemMgr ();
     virtual ~FGSystemMgr ();
+
     bool build (SGPropertyNode* config_props);
 };
 
diff --git a/src/Systems/vacuum.hxx b/src/Systems/vacuum.hxx
index 162c203d1..63287de87 100644
--- a/src/Systems/vacuum.hxx
+++ b/src/Systems/vacuum.hxx
@@ -40,11 +40,12 @@ public:
     VacuumSystem( int i );
     virtual ~VacuumSystem ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
 private:
     std::string _name;
diff --git a/src/Time/TimeManager.hxx b/src/Time/TimeManager.hxx
index 0f928a857..5b821e941 100644
--- a/src/Time/TimeManager.hxx
+++ b/src/Time/TimeManager.hxx
@@ -34,15 +34,19 @@ public:
     TimeManager();
     virtual ~TimeManager();
 
-    void computeTimeDeltas(double& simDt, double& realDt);
-
+    // Subsystem API.
     void init() override;
-    void reinit() override;
     void postinit() override;
+    void reinit() override;
     void shutdown() override;
     void unbind() override;
     void update(double dt) override;
 
+    // Subsystem identification.
+    static const char* subsystemName() { return "time"; }
+
+    void computeTimeDeltas(double& simDt, double& realDt);
+
     // SGPropertyChangeListener overrides
     void valueChanged(SGPropertyNode *) override;
 
@@ -51,8 +55,6 @@ public:
     inline double getMPProtocolClockSec() const { return _mpProtocolClock; }
     inline double getSteadyClockSec() const { return _steadyClock; }
 
-    static const char* subsystemName() { return "time"; }
-
 private:
     /**
      * Ensure a consistent update-rate using a combination of
diff --git a/src/Time/light.hxx b/src/Time/light.hxx
index 1d3443f9e..7fd88c13b 100644
--- a/src/Time/light.hxx
+++ b/src/Time/light.hxx
@@ -139,12 +139,12 @@ public:
     FGLight ();
     virtual ~FGLight ();
 
-    virtual void init ();
-    virtual void reinit ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update ( double dt );
-
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
 
     // Color related functions
 
diff --git a/src/Traffic/TrafficMgr.hxx b/src/Traffic/TrafficMgr.hxx
index 929602c26..3a790ac52 100644
--- a/src/Traffic/TrafficMgr.hxx
+++ b/src/Traffic/TrafficMgr.hxx
@@ -113,8 +113,10 @@ private:
 public:
     FGTrafficManager();
     ~FGTrafficManager();
-    void init();
-    void update(double time);
+
+    // Subsystem API.
+    void init() override;
+    void update(double time) override;
 
     FGScheduledFlightVecIterator getFirstFlight(const std::string &ref) { return flights[ref].begin(); }
     FGScheduledFlightVecIterator getLastFlight(const std::string &ref) { return flights[ref].end(); }
diff --git a/src/Viewer/view.hxx b/src/Viewer/view.hxx
index 591b5c2f8..1fb6d8af4 100644
--- a/src/Viewer/view.hxx
+++ b/src/Viewer/view.hxx
@@ -67,10 +67,10 @@ public:
     // Part 1: standard SGSubsystem implementation.
     //////////////////////////////////////////////////////////////////////
 
-    virtual void init ();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
+    void init() override;
+    void bind() override;
+    void unbind() override;
+    void update(double dt) override;
 
 
     //////////////////////////////////////////////////////////////////////
diff --git a/src/Viewer/viewmgr.hxx b/src/Viewer/viewmgr.hxx
index 14f763860..7a5f7f921 100644
--- a/src/Viewer/viewmgr.hxx
+++ b/src/Viewer/viewmgr.hxx
@@ -49,13 +49,17 @@ public:
     // Destructor
     ~FGViewMgr( void );
 
-    virtual void init ();
-    virtual void postinit();
-    virtual void bind ();
-    virtual void unbind ();
-    virtual void update (double dt);
-    virtual void reinit ();
-    virtual void shutdown();
+    // Subsystem API.
+    void bind() override;
+    void init() override;
+    void postinit() override;
+    void reinit() override;
+    void shutdown() override;
+    void unbind() override;
+    void update(double dt) override;
+
+    // Subsystem identification.
+    static const char* subsystemName() { return "view-manager"; }
 
     // getters
     inline int size() const { return views.size(); }
@@ -75,8 +79,6 @@ public:
 
     void add_view( flightgear::View * v );
 
-    static const char* subsystemName() { return "view-manager"; }
-
 private:
     simgear::TiedPropertyList _tiedProperties;
 
diff --git a/utils/fgpanel/FGPanel.cxx b/utils/fgpanel/FGPanel.cxx
index c5feb739a..45e7f0c1f 100644
--- a/utils/fgpanel/FGPanel.cxx
+++ b/utils/fgpanel/FGPanel.cxx
@@ -168,7 +168,7 @@ FGPanel::unbind () {
 }
 
 void
-FGPanel::update (const double dt) {
+FGPanel::update (double dt) {
   getInitDisplayList ();
   // Draw the instruments.
   // Syd Adams: added instrument clipping
diff --git a/utils/fgpanel/FGPanel.hxx b/utils/fgpanel/FGPanel.hxx
index 1be60898d..b08c7d1af 100644
--- a/utils/fgpanel/FGPanel.hxx
+++ b/utils/fgpanel/FGPanel.hxx
@@ -57,12 +57,11 @@ public:
     FGPanel (const SGPropertyNode_ptr root);
     virtual ~FGPanel ();
 
-    // Update the panel (every frame).
-    virtual void init ();
-    virtual void bind ();
-    virtual void unbind ();
-    //  virtual void draw ();
-    virtual void update (const double dt);
+    // Subsystem API.
+    void init() override;
+    void bind() override;
+    void unbind() override;
+    void update(double dt) override;
 
     // transfer pointer ownership!!!
     virtual void addInstrument (FGPanelInstrument * const instrument);
diff --git a/utils/fgpanel/FGPanelProtocol.hxx b/utils/fgpanel/FGPanelProtocol.hxx
index dec45f687..dc85e7fb2 100644
--- a/utils/fgpanel/FGPanelProtocol.hxx
+++ b/utils/fgpanel/FGPanelProtocol.hxx
@@ -33,11 +33,11 @@ class FGPanelProtocol : public SGSubsystem
 public:
     FGPanelProtocol (SGPropertyNode_ptr a_Root);
     virtual ~FGPanelProtocol ();
-    virtual void init ();
-    virtual void reinit ();
-    virtual void update (double dt);
 
-protected:
+    // Subsystem API.
+    void init() override;
+    void reinit() override;
+    void update(double dt) override;
 
 private:
     SGPropertyNode_ptr root;