Mach 6.7 ยท 354,200 ft
X-15 speed and altitude records
The X-15 holds two famous marks: Mach 6.7 and 354,200 ft. NASA's fact sheet lists both as unofficial, and the speed is widely cited as the fastest ever recorded by a crewed, powered aircraft.
| Record | Value | Pilot | Date and flight | Aircraft |
|---|---|---|---|---|
| Speed | Mach 6.7, 4,520 mph (at 102,100 ft) | Pete Knight | 3 October 1967, flight 188 | X-15A-2 |
| Altitude | 354,200 ft (67.1 miles) | Joe Walker | 22 August 1963, flight 91 | X-15-3 |
The speed record
The standard X-15 reached Mach 6.04 on 9 November 1961, flown by Robert White. Mach 6.7 needed the rebuilt X-15A-2, with its longer fuselage, external tanks and ablative coating. Pete Knight flew it on 3 October 1967. The aircraft was carrying a dummy ramjet engine on a pylon and came back with heat damage. Walker's fastest flight was flight 59 on 27 June 1962, at 4,104 mph.
The altitude record
Joe Walker flew 354,200 ft on 22 August 1963, a month after flight 90 reached 347,800 ft. Those are the only two X-15 flights above 328,000 ft (100 km), the line the international aeronautics federation (FAI) uses for space.
Astronaut wings: the 50-mile line
The US Air Force recognised 50 miles (264,000 ft) as the edge of space. Thirteen X-15 flights went above it, by eight pilots: Dana, Engle, Knight, McKay, Rushworth, Walker, White and Adams. The five Air Force pilots already held astronaut wings; Michael Adams, killed on flight 191 at 266,000 ft, received his posthumously. In 2005 NASA gave its own wings to Dana, McKay (posthumously) and Walker.
Milestones on the way up
| Milestone | Date |
|---|---|
| Mach 4 | 7 March 1961 |
| Mach 5 | 23 June 1961 |
| 200,000 ft | 11 October 1961 |
| Mach 6 | 9 November 1961 |
| 300,000 ft | 17 July 1962 |
| 100 km | 19 July 1963 |
| Mach 6.7 | 3 October 1967 |
Each is in the X-15 timeline with context.
Chase the records in the simulator
Project X-15's record challenge tracks the same two marks on every full flight from the B-52, with a best-ever mark saved in your browser. Try to match Walker and White.