On October 14, 1947, Chuck Yeager (1923–) broke the sound barrier in his Bell X-1 test plane, “Glamorous Glennis.” In order to reach the sound barrier, the X-1 was carried in the belly of a B-29 bomber to an altitude of 3,658 meters (12,000 feet) where it was dropped. The X-1’s rocket engine ignited and Yeager took the plane to an altitude of 13,106 meters (43,000 feet). At this altitude, Yeager was able to break the sound barrier by traveling 660 miles per hour. The X-1 experienced a turbulent set of compression waves just before he broke past the barrier at Mach 1.05. Yeager kept the plane at this supersonic speed for a few moments before he cut off the rocket engine and headed back toward Earth.