Beskrivning : FDC. 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. As of September 2015, the X-15 holds the official world record for the highest speed ever reached by a manned, powered aircraft. Its maximum speed was 4,520 miles per hour (7,274 km/h), or Mach 6.72.