June 29, 1965: Astronaut Engle Breaks X-15 Record Published June 29, 2020 U.S. Air Force/NASA EDWARDS AIR FORCE BASE, Calif -- Captain Joseph Engle reached 280,600 feet (53 miles) in the X-15 No. 3, becoming the third Air Force winged astronaut, the youngest pilot, and the first civilian to receive astronaut wings. He went on to fly two other X-15 flights that would have qualified him for this honor. 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's official world record for the highest speed ever recorded by a crewed, powered aircraft, set in October 1967 when William J. Knight flew at Mach 6.70 at 102,100 feet (31,120 m), a speed of 4,520 miles per hour (7,274 km/h; 2,021 m/s), and has remained unbroken as of 2020. Retired USAF Major General Joe Henry Engle is an American pilot, aeronautical engineer and former astronaut. He was the commander of two Space Shuttle missions including STS-2, the program's second orbital flight. He also participated in the Shuttle program's Approach and Landing Tests. Engle is one of twelve pilots who flew the North American X-15, an experimental spaceplane jointly operated by the Air Force and NASA. As an X-15 pilot, Engle made three flights above 50 miles, thus qualifying for astronaut wings under the American convention for the boundary of space. In 1966, he was selected for NASA's fifth Astronaut Group, joining the Apollo program. He was the backup Lunar Module Pilot (LMP) for Apollo 14 and originally scheduled as LMP for Apollo 17. However, cancellation of later flights prompted NASA to select geologist-astronaut Harrison Schmitt as LMP, displacing Engle. Engle is an experienced spaceplane operator and the last living X-15 pilot.