 Modern cruise missiles are capable of travelling at supersonic or high subsonic speeds, are self-navigating, and are able to fly on a non-ballistic, extremely low-altitude trajectory.The idea of an "aerial torpedo" was shown in the British 1909 film "The Airship Destroyer", where flying torpedoes controlled wirelessly are used to bring down airships bombing London.In 1916, American aviator Lawrence Sperry built and patented an "aerial torpedo", the Hewitt-Sperry Automatic Airplane, a small biplane carrying a TNT charge, a Sperry autopilot and a barometric altitude control.