• The X-1 was the first aircraft to break the sound barrier in level flight.

   The Bell X-1 was the first aircraft to fly faster than the speed of sound, something said to be impossible at the time. Three X-1 aircraft were built, X-1-1, X-1-2, and X-1-3. X-1-1 was powered by an XLR-11 rocket engine and was launched from a B-29A mothership. Its first powered flight occurred on April 11, 1946 with Chalmers Goodlin at the controls. On October 14, 1947, USAF Captain Charles "Chuck" Yeager flew the X-1-1 through the sound barrier and into the history books. He hit a top speed of Mach 1.06 (700mph) and an altitude of 43,000 feet. The X-1-1 hit a maximum speed of Mach 1.45 throughout its life and a top altitude of 71,902 feet. X-1-2 would later become retired to be rebuilt as the X-1E, and the X-1-3 saw its last days when it blew up under its launch plane, a B-50, during ground static operations at Edwards AFB, California.

   The X-1A pushed the records a bit further, as it hit 90,440 feet on August 26, 1954. The X-1A would later explode in the desert after an explosion before launch left its landing gear crippled. Its pilot and the B-29 crew returned to base alive.

   After the X-1-2 converted to the new X-1E variant, it could fly almost twice as fast as the original X-1-2. The X-1E was powered by a Reaction Motors, Inc. LR-8-RM-5 four chambered rocket engine.