One of the world’s most successful aeronautical test programs, the hypersonic X-15 aircraft completed 199 flights and established numerous records for speed and altitude – including the absolute speed record for winged aircraft at Mach 6.7. Rare limited edition commemorative cover no. 1117 of 1500 flown over Edwards AFB by Joe Engle, 9.5 x 4, with a color cachet honoring X-15 Rocket Pilots 1959–1999, signed in pencil by Robert White, Scott Crossfield, William Pete Knight, Bill Dana, and Joe Engle. In fine condition. R&R COA.
