After the war, American test pilots filed reports about the Me 262, including the possibility of a speed of Mach 1. Compressibility in pitot tubes of the time often resulted in exaggerated speed readings near the speed of sound, particularly in German equipment, which was adversely affected by supply shortages as the war progressed. American Sabrejets and other high-speed aircraft (including the Bell X-1) also experienced anomalous airspeed readings in the high-subsonic flight regime (between 0.8 Mach and Mach 1). The Me 262's pre-area rule fuselage would have additionally resulted in very high transonic drag, and its engines were already underpowered and temperamental to begin with. However, aircraft such as the Bell X-1, F-86 Sabre and Convair F2Y Sea Dart similarly did not have area ruled fuselages, yet are acknowledged to have flown at supersonic speeds — here the engine thrust, either alone or in combination with the pull of gravity during a dive, supplies enough force to accelerate the airplane to supersonic speed.