The North American X-15 was a hypersonic rocket-powered aircraft operated by the United States Air Force and the National Aeronautics and Space Administration as part of the X-plane series of experimental aircraft. The X-15 set speed and altitude records in the 1960s, reaching the edge of outer space and returning with valuable data used in aircraft and spacecraft design. , the X-15 holds the official world record for the highest speed ever reached by a manned, powered aircraft. Its maximum speed was , or Mach 6.72.