X-15

The North American X-15 is a hypersonic rocket-powered aircraft operated by the United States Air Force and the National Aeronautics and Space Administration (better known as NASA) as part of the X-plane series of experimental aircraft. The X-15 set speed and altitude records in the 1960s, crossing the edge of outer space and returning with valuable data used in aircraft and spacecraft design. The X-15's highest speed, , was achieved on 3October 1967, when William J. Knight flew at Mach6.7 at an altitude of , or 19.34miles. This set the official world record for the highest speed ever recorded by a crewed, powered aircraft, which remains unbroken.