The Lockheed Martin F-35 Lightning II is not just a stealthy sensor node with wings attached, but it is also a supersonic fighter built to sprint when the mission demands it. The number most people cite is the aircraft’s maximum speed of around Mach 1.6, but that headline figure hides the realities of how jets actually fly. The aircraft’s top speed changes with altitude and outside air temperature, and it changes depending on the kind of munitions payload the aircraft has with it.