diff --git a/src/ATC/tower.cxx b/src/ATC/tower.cxx
index 25801f5d6..4b8115df6 100644
--- a/src/ATC/tower.cxx
+++ b/src/ATC/tower.cxx
@@ -1109,6 +1109,8 @@ void FGTower::CheckCircuitList(double dt) {
 			circuitListItr = circuitList.erase(circuitListItr);
 			if(circuitListItr == circuitList.end() ) {
 				circuitListItr = circuitList.begin();
+				// avoid increment of circuitListItr (would increment to second element, or crash if no element left)
+				return;
 			}
 		}
 		++circuitListItr;
diff --git a/src/Environment/fgclouds.cxx b/src/Environment/fgclouds.cxx
index f6c526403..75a9b6417 100644
--- a/src/Environment/fgclouds.cxx
+++ b/src/Environment/fgclouds.cxx
@@ -263,7 +263,7 @@ void FGClouds::buildMETAR(void) {
 
 // copy from FGMetarEnvironmentCtrl until better
 void
-FGClouds::update_metar_properties( FGMetar *m )
+FGClouds::update_metar_properties( const FGMetar *m )
 {
     int i;
     double d;
diff --git a/src/Environment/fgclouds.hxx b/src/Environment/fgclouds.hxx
index e5840fbe1..ae555b363 100644
--- a/src/Environment/fgclouds.hxx
+++ b/src/Environment/fgclouds.hxx
@@ -51,7 +51,7 @@ private:
 
 	void setLayer( int iLayer, float alt_m, const string& coverage, const string& layer_type );
 
-	void update_metar_properties( FGMetar *m );
+	void update_metar_properties( const FGMetar *m );
 
 	void FGClouds::update_env_config ();
 
diff --git a/src/Traffic/TrafficMgr.cxx b/src/Traffic/TrafficMgr.cxx
index 1e3b73a2c..3d7fe4d79 100644
--- a/src/Traffic/TrafficMgr.cxx
+++ b/src/Traffic/TrafficMgr.cxx
@@ -85,7 +85,6 @@ void FGTrafficManager::init()
 	{
 	  currAircraft=scheduledAircraft.erase(currAircraft);
 	  //cerr << "Erasing " << currAircraft->getRegistration() << endl;
-	  currAircraft--;
 	}
       else 
 	{
@@ -102,6 +101,8 @@ void FGTrafficManager::init()
 void FGTrafficManager::update(double something)
 {
   time_t now = time(NULL) + fgGetLong("/sim/time/warp");
+  if (scheduledAircraft.size() == 0)
+	  return;
   if(currAircraft == scheduledAircraft.end())
     {
       //cerr << "resetting schedule " << endl;