The X-24A made its last of 28 flights on June 4, 1971. In January 1972 the conversion to X-24B was started, the aircraft being stripped to its basic structure and rebuilt with completely new external lines, as seen in a Martin Marietta photo.
The X-24B made its first unpowered flight on August 1 1973, and its
first powered flight on November 15, 1973. The X-24B made the last of
36 flights on November 26, 1975, a maximum speed of Mach 1.752
(1,299.029 mph, 2,090.585 kmh) and an altitude of 74,130 ft (22,595 m)
were attained. The aircraft was donated to the USAF Museum at
Wright-Patterson AFB in November 1976.
Both the X-24A and X-24B were carried by a B-52 to 45,000 ft (13,716
m) and than released for a powered or unpowered flight.