diff --git a/src/Aircraft/continuous.cxx b/src/Aircraft/continuous.cxx
index 632d73a96..30512adbc 100644
--- a/src/Aircraft/continuous.cxx
+++ b/src/Aircraft/continuous.cxx
@@ -187,7 +187,37 @@ static bool ReadFGReplayData2(
     return true;
 }
 
-std::unique_ptr<FGReplayData> ReadFGReplayData(
+/* Removes items more than <n> away from <it>. <n> can be -ve. */
+template<typename Container, typename Iterator>
+static void remove_far_away(Container& container, Iterator it, int n)
+{
+    SG_LOG(SG_GENERAL, SG_DEBUG, "container.size()=" << container.size());
+    if (n > 0)
+    {
+        for (int i=0; i<n; ++i)
+        {
+            if (it == container.end())  return;
+            ++it;
+        }
+        container.erase(it, container.end());
+    }
+    else
+    {
+        for (int i=0; i<-n-1; ++i)
+        {
+            if (it == container.begin())    return;
+            --it;
+        }
+        container.erase(container.begin(), it);
+    }
+    SG_LOG(SG_GENERAL, SG_DEBUG, "container.size()=" << container.size());
+}
+
+/* Returns FGReplayData for frame at specified position in file. Uses
+continuous.m_in_pos_to_frame as a cache, and trims this cache using
+remove_far_away(). */
+static std::shared_ptr<FGReplayData> ReadFGReplayData(
+        Continuous& continuous,
         std::ifstream& in,
         size_t pos,
         SGPropertyNode* config,
@@ -197,40 +227,83 @@ std::unique_ptr<FGReplayData> ReadFGReplayData(
         int in_compression
         )
 {
-    /* Need to clear any eof bit, otherwise seekg() will not work (which is
-    pretty unhelpful). E.g. see:
-        https://stackoverflow.com/questions/16364301/whats-wrong-with-the-ifstream-seekg
-    */
-    SG_LOG(SG_SYSTEMS, SG_BULK, "reading frame. pos=" << pos);
-    in.clear();
-    in.seekg(pos);
+    std::shared_ptr<FGReplayData>   ret;
+    auto it = continuous.m_in_pos_to_frame.find(pos);
     
-    std::unique_ptr<FGReplayData>   ret(new FGReplayData);
-
-    readRaw(in, ret->sim_time);
-    if (!in)
+    if (it != continuous.m_in_pos_to_frame.end())
     {
-        SG_LOG(SG_SYSTEMS, SG_DEBUG, "Failed to read fgtape frame at offset " << pos);
-        return nullptr;
+        if (0
+            || (load_signals && !it->second->load_signals)
+            || (load_multiplayer && !it->second->load_multiplayer)
+            || (load_extra_properties && !it->second->load_extra_properties)
+            )
+        {
+            /* This frame is in the continuous.m_in_pos_to_frame cache, but
+            doesn't contain all of the required items, so we need to reload. */
+            continuous.m_in_pos_to_frame.erase(it);
+            it = continuous.m_in_pos_to_frame.end();
+        }
     }
-    bool ok;
-    if (in_compression)
+    if (it == continuous.m_in_pos_to_frame.end())
     {
-        uint8_t     flags;
-        uint32_t    compressed_size;
-        in.read((char*) &flags, sizeof(flags));
-        in.read((char*) &compressed_size, sizeof(compressed_size));
-        simgear::ZlibDecompressorIStream    in_decompress(in, SGPath(), simgear::ZLibCompressionFormat::ZLIB_RAW);
-        ok = ReadFGReplayData2(in_decompress, config, load_signals, load_multiplayer, load_extra_properties, ret.get());
+        /* Load FGReplayData at offset <pos>.
+
+        We need to clear any eof bit, otherwise seekg() will not work (which is
+        pretty unhelpful). E.g. see:
+            https://stackoverflow.com/questions/16364301/whats-wrong-with-the-ifstream-seekg
+        */
+        SG_LOG(SG_SYSTEMS, SG_BULK, "reading frame. pos=" << pos);
+        in.clear();
+        in.seekg(pos);
+
+        ret.reset(new FGReplayData);
+
+        readRaw(in, ret->sim_time);
+        if (!in)
+        {
+            SG_LOG(SG_SYSTEMS, SG_DEBUG, "Failed to read fgtape frame at offset " << pos);
+            return nullptr;
+        }
+        bool ok;
+        if (in_compression)
+        {
+            uint8_t     flags;
+            uint32_t    compressed_size;
+            in.read((char*) &flags, sizeof(flags));
+            in.read((char*) &compressed_size, sizeof(compressed_size));
+            simgear::ZlibDecompressorIStream    in_decompress(in, SGPath(), simgear::ZLibCompressionFormat::ZLIB_RAW);
+            ok = ReadFGReplayData2(in_decompress, config, load_signals, load_multiplayer, load_extra_properties, ret.get());
+        }
+        else
+        {
+            ok = ReadFGReplayData2(in, config, load_signals, load_multiplayer, load_extra_properties, ret.get());
+        }
+        if (!ok)
+        {
+            SG_LOG(SG_SYSTEMS, SG_DEBUG, "Failed to read fgtape frame at offset " << pos);
+            return nullptr;
+        }
+        it = continuous.m_in_pos_to_frame.lower_bound(pos);
+        it = continuous.m_in_pos_to_frame.insert(it, std::make_pair(pos, ret));
+        
+        /* Delete faraway items. */
+        size_t size_old = continuous.m_in_pos_to_frame.size();
+        int n = 2;
+        size_t size_max = 2*n - 1;
+        remove_far_away(continuous.m_in_pos_to_frame, it, n);
+        remove_far_away(continuous.m_in_pos_to_frame, it, -n);
+        size_t size_new = continuous.m_in_pos_to_frame.size();
+        SG_LOG(SG_GENERAL, SG_DEBUG, ""
+                << " n=" << size_old
+                << " size_max=" << size_max
+                << " size_old=" << size_old
+                << " size_new=" << size_new
+                );
+        assert(size_new <= size_max);
     }
     else
     {
-        ok = ReadFGReplayData2(in, config, load_signals, load_multiplayer, load_extra_properties, ret.get());
-    }
-    if (!ok)
-    {
-        SG_LOG(SG_SYSTEMS, SG_DEBUG, "Failed to read fgtape frame at offset " << pos);
-        return nullptr;
+        ret = it->second;
     }
     return ret;
 }
@@ -514,7 +587,17 @@ SGPropertyNode_ptr continuousWriteHeader(
     return config;
 }
 
-bool replayContinuousInternal(
+/* Replays one frame from Continuous recording. <offset> and <offset_old> are
+offsets in file of frames that are >= and < <time> respectively. <offset_old>
+may be 0, in which case it is ignored.
+
+We load the frame(s) from disc, omitting some data depending on
+replay_signals, replay_multiplayer and replay_extra_properties. Then call
+m_pRecorder->replay(), which updates the global state.
+
+Returns true on success, otherwise we failed to read from Continuous recording.
+*/
+static bool replayContinuousInternal(
         Continuous& continuous,
         FGFlightRecorder* recorder,
         double time,
@@ -529,7 +612,8 @@ bool replayContinuousInternal(
         int* ysize
         )
 {
-    std::unique_ptr<FGReplayData> replay_data = ReadFGReplayData(
+    std::shared_ptr<FGReplayData> replay_data = ReadFGReplayData(
+            continuous,
             continuous.m_in,
             offset,
             continuous.m_in_config,
@@ -544,10 +628,11 @@ bool replayContinuousInternal(
         return false;
     }
     assert(replay_data.get());
-    std::unique_ptr<FGReplayData> replay_data_old;
+    std::shared_ptr<FGReplayData> replay_data_old;
     if (offset_old)
     {
         replay_data_old = ReadFGReplayData(
+                continuous,
                 continuous.m_in,
                 offset_old,
                 continuous.m_in_config,
@@ -557,11 +642,12 @@ bool replayContinuousInternal(
                 continuous.m_in_compression
                 );
     }
-    if (replay_extra_properties) SG_LOG(SG_SYSTEMS, SG_BULK,
+    if (replay_extra_properties) SG_LOG(SG_SYSTEMS, SG_DEBUG,
             "replay():"
             << " time=" << time
             << " offset=" << offset
             << " offset_old=" << offset_old
+            << " replay_data_old=" << replay_data_old
             << " replay_data->raw_data.size()=" << replay_data->raw_data.size()
             << " replay_data->multiplayer_messages.size()=" << replay_data->multiplayer_messages.size()
             << " replay_data->extra_properties.size()=" << replay_data->extra_properties.size()
@@ -733,12 +819,19 @@ bool replayContinuous(FGReplayInternal& self, double time)
 
         if (replay_this_frame)
         {
+            size_t pos_prev = 0;
+            if (p_before != self.m_continuous->m_in_time_to_frameinfo.begin())
+            {
+                auto p_before_prev = p_before;
+                --p_before_prev;
+                pos_prev = p_before_prev->second.offset;
+            }
             bool ok = replayContinuousInternal(
                     *self.m_continuous,
                     self.m_flight_recorder.get(),
                     p_before->first,
                     p_before->second.offset,
-                    0 /*offset_old*/,
+                    pos_prev /*offset_old*/,
                     false /*replay_signals*/,
                     p_before->first > time - multiplayer_recent /*replay_multiplayer*/,
                     true /*replay_extra_properties*/,
diff --git a/src/Aircraft/continuous.hxx b/src/Aircraft/continuous.hxx
index f4a06864e..51b414667 100644
--- a/src/Aircraft/continuous.hxx
+++ b/src/Aircraft/continuous.hxx
@@ -27,6 +27,8 @@ struct Continuous : SGPropertyChangeListener
     SGPropertyNode_ptr              m_in_config;
     double                          m_in_time_last = 0;
     double                          m_in_frame_time_last = 0;
+    std::map<size_t, std::shared_ptr<FGReplayData>>
+                                    m_in_pos_to_frame;
     
     std::ifstream                   m_indexing_in;
     std::streampos                  m_indexing_pos;
@@ -48,29 +50,15 @@ struct Continuous : SGPropertyChangeListener
     int                 m_in_compression = 0;
 };
 
-// Attempts to load Continuous recording header properties into
-// <properties>. If in is null we use internal std::fstream, otherwise we
-// use *in.
-//
-// Returns 0 on success, +1 if we may succeed after further download, or -1
-// if recording is not a Continuous recording.
-//
+/* Attempts to load Continuous recording header properties into
+<properties>. If in is null we use internal std::fstream, otherwise we use *in.
+
+Returns 0 on success, +1 if we may succeed after further download, or -1 if
+recording is not a Continuous recording. */
 int loadContinuousHeader(const std::string& path, std::istream* in, SGPropertyNode* properties);
 
 
-// Reads all or part of a FGReplayData from Continuous file.
-std::unique_ptr<FGReplayData> ReadFGReplayData(
-        std::ifstream& in,
-        size_t pos,
-        SGPropertyNode* config,
-        bool load_signals,
-        bool load_multiplayer,
-        bool load_extra_properties,
-        int in_compression
-        );
-
-// Writes one frame of continuous record information.
-//
+/* Writes one frame of continuous record information. */
 bool continuousWriteFrame(
         Continuous& continuous,
         FGReplayData* r,
@@ -78,18 +66,17 @@ bool continuousWriteFrame(
         SGPropertyNode_ptr config
         );
 
-// Opens continuous recording file and writes header.
-//
-// If MetaData is unset, we initialise it by calling saveSetup(). Otherwise
-// should be already set up.
-//
-// If Config is unset, we make it point to a new node populated by
-// m_pRecorder->getConfig(). Otherwise it should be already set up to point to
-// such information.
-//
-// If path_override is not "", we use it as the path (instead of the path
-// determined by saveSetup().
-//
+/* Opens continuous recording file and writes header.
+
+If MetaData is unset, we initialise it by calling saveSetup(). Otherwise should
+be already set up.
+
+If Config is unset, we make it point to a new node populated by
+m_pRecorder->getConfig(). Otherwise it should be already set up to point to
+such information.
+
+If path_override is not "", we use it as the path (instead of the path
+determined by saveSetup(). */
 SGPropertyNode_ptr continuousWriteHeader(
         Continuous&         continuous,
         FGFlightRecorder*   m_pRecorder,
@@ -98,32 +85,12 @@ SGPropertyNode_ptr continuousWriteHeader(
         FGTapeType          tape_type
         );
 
-// Replays one frame from Continuous recording. <offset> and <offset_old>
-// are offsets in file of frames that are >= and < <time> respectively.
-// <offset_old> may be 0, in which case it is ignored.
-//
-// We load the frame(s) from disc, omitting some data depending on
-// replay_signals, replay_multiplayer and replay_extra_properties. Then call
-// m_pRecorder->replay(), which updates the global state.
-//
-// Returns true on success, otherwise we failed to read from Continuous
-// recording.
-//
-bool replayContinuousInternal(
-        Continuous& continuous,
-        FGFlightRecorder* recorder,
-        double time,
-        size_t offset,
-        size_t offset_old,
-        bool replay_signals,
-        bool replay_multiplayer,
-        bool replay_extra_properties,
-        int* xpos,
-        int* ypos,
-        int* xsize,
-        int* ysize
-        );
+/* Replays one frame from Continuous recording.
 
+Returns true on success, otherwise we failed to read from Continuous recording.
+*/
 bool replayContinuous(FGReplayInternal& self, double time);
 
+/* Stops any video recording that was started because of
+continuous->m_replay_create_video. */
 void continuous_replay_video_end(Continuous& continuous);
diff --git a/src/Aircraft/flightrecorder.cxx b/src/Aircraft/flightrecorder.cxx
index dd1e1c42e..2bb10a902 100644
--- a/src/Aircraft/flightrecorder.cxx
+++ b/src/Aircraft/flightrecorder.cxx
@@ -737,6 +737,83 @@ static void setInt(const std::string& value, int* out)
     }
 }
 
+/* Converts string to double, writing to out-para <out> and setting <ok> to
+true. If conversion fails or fails to use the entire input string, sets ok to
+false. */
+static void string_to_double(const std::string& s, double& out, bool& ok)
+{
+    errno = 0;
+    char* end;
+    out = strtod(s.c_str(), &end);
+    if (errno || !end || *end != 0)
+    {
+        ok = false;
+        return;
+    }
+    ok = true;
+}
+
+/* Updates property <path> to <value_next_string>. If property is also in
+<frame_prev> and values look like floating point, we interpolate using <ratio>.
+*/
+static void replayProperty(
+        const std::string& path,
+        const std::string& value_next_string,
+        const FGReplayData* frame_prev,
+        double ratio
+        )
+{
+    SGPropertyNode* p = globals->get_props()->getNode(path, true /*create*/);
+    bool done = false;
+    if (frame_prev)
+    {
+        /* Check whether <path> is in frame_prev's list of property changes. */
+        SG_LOG(SG_SYSTEMS, SG_DEBUG, "p && _pLastBuffer");
+        auto p_prev_it = frame_prev->replay_extra_property_changes.find(path);
+        if (p_prev_it != frame_prev->replay_extra_property_changes.end())
+        {
+            /* Property <path> is also in frame_prev. */
+            SG_LOG(SG_SYSTEMS, SG_DEBUG, "property in frame_prev and frame_next:"
+                    << " " << path);
+            const std::string&  value_prev_string = p_prev_it->second;
+            bool value_prev_ok;
+            bool value_next_ok;
+            double value_prev;
+            double value_next;
+            string_to_double(value_prev_string, value_prev, value_prev_ok);
+            string_to_double(value_next_string, value_next, value_next_ok);
+            if (value_prev_ok && value_next_ok)
+            {
+                /* Both values look like floating point so we interpolate. */
+                SG_LOG(SG_SYSTEMS, SG_DEBUG, "property is fp");
+                TInterpolation  interpolation = TInterpolation::linear;
+                if (simgear::strutils::ends_with(path, "-deg"))
+                {
+                    interpolation = TInterpolation::angular_deg;
+                }
+                else if (simgear::strutils::ends_with(path, "-rad"))
+                {
+                    interpolation = TInterpolation::angular_rad;
+                }
+                SG_LOG(SG_SYSTEMS, SG_DEBUG, "calling weighting() ratio=" << ratio);
+                double value_interpolated = weighting(
+                        interpolation,
+                        ratio,
+                        value_prev,
+                        value_next
+                        );
+                SG_LOG(SG_GENERAL, SG_DEBUG, "Interpolating " << path
+                        << ": [" << value_prev << " .. " << value_next
+                        << "] => " << value_interpolated
+                        );
+                globals->get_props()->setDoubleValue(path, value_interpolated);
+                done = true;
+            }
+        }
+    }
+    if (!done) p->setStringValue(path, value_next_string);
+}
+
 /** Replay.
  * Restore all properties with data from given buffer. */
 void
@@ -750,11 +827,10 @@ FGFlightRecorder::replay(double SimTime, const FGReplayData* _pNextBuffer,
 {
     const char* pLastBuffer = (_pLastBuffer && !_pLastBuffer->raw_data.empty()) ? &_pLastBuffer->raw_data.front() : nullptr;
     const char* pBuffer = (_pNextBuffer && !_pNextBuffer->raw_data.empty()) ? &_pNextBuffer->raw_data.front() : nullptr;
-    
+    double ratio = 1.0;
     if (pBuffer) {
         /* Replay signals. */
         int Offset = 0;
-        double ratio = 1.0;
         if (pLastBuffer)
         {
             double NextSimTime = _pNextBuffer->sim_time;
@@ -953,13 +1029,57 @@ FGFlightRecorder::replay(double SimTime, const FGReplayData* _pNextBuffer,
             if (replay_main_view) {
                 SG_LOG(SG_SYSTEMS, SG_DEBUG, "SimTime=" << SimTime
                         << " replaying view change: " << path << "=" << value);
-                globals->get_props()->setStringValue(path, value);
+                /* Interpolate floating point values if possible. */
+                replayProperty(path, value, _pLastBuffer, ratio);
             }
         }
         else if (replay_extra_properties) {
             SG_LOG(SG_SYSTEMS, SG_DEBUG, "SimTime=" << SimTime
                     << " replaying extra_property change: " << path << "=" << value);
-            globals->get_props()->setStringValue(path, value);
+            SGPropertyNode* p = globals->get_props()->getNode(path, true /*create*/);
+            bool done = false;
+            if (p && _pLastBuffer) {
+                SG_LOG(SG_SYSTEMS, SG_DEBUG, "p && _pLastBuffer");
+                auto p_prev_it = _pLastBuffer->replay_extra_property_changes.find(path);
+                if (p_prev_it != _pLastBuffer->replay_extra_property_changes.end()) {
+                    /* Property <path> is in both _pLastBuffer and
+                    _pNextBuffer, so if it is floating point, we will
+                    interpolate. */
+                    SG_LOG(SG_SYSTEMS, SG_DEBUG, "property in _pLastBuffer and _pNextBuffer:"
+                            << " " << path);
+                    const std::string&  valus_prev = p_prev_it->second;
+                    size_t  value_prev_len;
+                    size_t  value_next_len;
+                    double value_prev = std::stod(valus_prev, &value_prev_len);
+                    double value_next = std::stod(value, &value_next_len);
+                    if (value_prev_len == valus_prev.size() && value_next_len == value.size()) {
+                        /* Both values look like floating point so we will
+                        interpolate. */
+                        SG_LOG(SG_SYSTEMS, SG_DEBUG, "property is fp");
+                        TInterpolation  interpolation = TInterpolation::linear;
+                        if (simgear::strutils::ends_with(path, "-deg")) {
+                            interpolation = TInterpolation::angular_deg;
+                        }
+                        else if (simgear::strutils::ends_with(path, "-rad")) {
+                            interpolation = TInterpolation::angular_rad;
+                        }
+                        SG_LOG(SG_SYSTEMS, SG_DEBUG, "calling weighting()");
+                        double value_interpolated = weighting(
+                                interpolation,
+                                ratio,
+                                value_prev,
+                                value_next
+                                );
+                        SG_LOG(SG_GENERAL, SG_DEBUG, "Interpolating " << path
+                                << ": [" << value_prev << " .. " << value_next
+                                << "] => " << value_interpolated
+                                );
+                        globals->get_props()->setDoubleValue(path, value_interpolated);
+                        done = true;
+                    }
+                }
+            }
+            if (!done) p->setStringValue(path, value);
         }
     }
 }
diff --git a/src/Aircraft/replay-internal.hxx b/src/Aircraft/replay-internal.hxx
index 524e94e27..1c3004f96 100644
--- a/src/Aircraft/replay-internal.hxx
+++ b/src/Aircraft/replay-internal.hxx
@@ -46,6 +46,10 @@ extern const char* const FlightRecorderFileMagic;
 /* Data for a single frame. */
 struct FGReplayData
 {
+    bool load_signals;
+    bool load_multiplayer;
+    bool load_extra_properties;
+    
     double sim_time;
     
     // Our aircraft state.