In June 1962 this, the second of three X-15s, became the first aircraft to exceed Mach 5 after being air-dropped form its NB-52A mothership over Mud Lake, NV. In October 1967, after a fuselage stretch and addition of the large propellant tanks, it reached Mach 6.7, fastest of the three X-15s. After service, 56-6671 went into storage till moved to the USAFM in 1969.

As a kid in the 1960s I can well remember being inspired by this extraordinary rocket-powered machine built to investigate the effects of hypersonic flight. In June 1962 this, the second of three X-15s, became the first aircraft to exceed Mach 5 after being air-dropped form its NB-52A mothership over Mud Lake, NV. In October 1967, after a fuselage stretch and addition of the large propellant tanks, it reached Mach 6.7, fastest of the three X-15s. In December 1968 the 200th X-15 flight was cancelled and 56-6671 went into storage till moved to the USAFM the following year

This was the second of three X-15 a/c. After a mishap, it was rebuilt into an improved version. This included external propellant tanks for longer burn time and a slightly longer fuselage. In October 1967, being flown by Pete Knight, this X-15 set a speed record of Mach 6.7 (4,520 miles per hour) which still stands today. Transferred to the museum in 1969 after the X-15 program ended.