Air-launched at an altitude of 7,000
meters (23,000 feet) from the bomb
bay of a Boeing B-29, the X-1 used
its rocket engine to climb to its
test altitude. It flew a total of 78 times,
and on March 26, 1948,
with Yeager at the controls, it attained a
speed of 1,540 kilometers (957
miles) per hour, Mach 1.45, at an altitude
of 21,900 meters (71,900
feet). This was the highest velocity and altitude
reached by a manned
airplane up to that time. Transferred from
the U.S. Air Force.