North American X-15

The North American X-15 is a hypersonicrocket-powered aircraft formerly operated by the United States Air Force and the National Aeronautics and Space Administration (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, 4,520 miles per hour (7,274 km/h; 2,021 m/s), was achieved on 3October 1967, when William J. Knight flew at Mach6.7 at an altitude of 102,100 feet (31,120 m), or 19.34miles. This set the official world record for the highest speed ever recorded by a crewed, powered aircraft and remains unbroken.

During the X-15 program, 12pilots flew a combined 199flights. Of these, 8 pilots flew a combined 13flights which met the Air Force spaceflight criterion by exceeding the altitude of 50 miles (80 km), thus qualifying these pilots as being astronauts; of those 13flights, 2 (flown by the same civilian pilot) met the FAI definition (100 kilometres (62 mi)) of outer space. The 5Air Force pilots qualified for military astronaut wings immediately, while the 3civilian pilots were eventually awarded NASA astronaut wings in 2005, 35years after the last X-15 flight.