diff --git a/libraries/AP_AHRS/AP_AHRS.h b/libraries/AP_AHRS/AP_AHRS.h
index ea4e96ff97..fe9e98738c 100644
--- a/libraries/AP_AHRS/AP_AHRS.h
+++ b/libraries/AP_AHRS/AP_AHRS.h
@@ -115,6 +115,38 @@ public:
         return _flags.fly_forward;
     }
 
+    /*
+      set the "likely flying" flag. This is not guaranteed to be
+      accurate, but is the vehicle codes best guess as to the whether
+      the vehicle is currently flying
+     */
+    void set_likely_flying(bool b) {
+        if (b && !_flags.likely_flying) {
+            _last_flying_ms = AP_HAL::millis();
+        }
+        _flags.likely_flying = b;
+    }
+
+    /*
+      get the likely flying status. Returns true if the vehicle code
+      thinks we are flying at the moment. Not guaranteed to be
+      accurate
+     */
+    bool get_likely_flying(void) const {
+        return _flags.likely_flying;
+    }
+
+    /*
+      return time in milliseconds since likely_flying was set
+      true. Returns zero if likely_flying is currently false
+    */
+    uint32_t get_time_flying_ms(void) const {
+        if (!_flags.likely_flying) {
+            return 0;
+        }
+        return AP_HAL::millis() - _last_flying_ms;
+    }
+    
     AHRS_VehicleClass get_vehicle_class(void) const {
         return _vehicle_class;
     }
@@ -551,8 +583,12 @@ protected:
         uint8_t fly_forward             : 1;    // 1 if we can assume the aircraft will be flying forward on its X axis
         uint8_t correct_centrifugal     : 1;    // 1 if we should correct for centrifugal forces (allows arducopter to turn this off when motors are disarmed)
         uint8_t wind_estimation         : 1;    // 1 if we should do wind estimation
+        uint8_t likely_flying           : 1;    // 1 if vehicle is probably flying
     } _flags;
 
+    // time when likely_flying last went true
+    uint32_t _last_flying_ms;
+
     // calculate sin/cos of roll/pitch/yaw from rotation
     void calc_trig(const Matrix3f &rot,
                    float &cr, float &cp, float &cy,