<P> The British Air Ministry signed an agreement with the United States to exchange all its high - speed research, data and designs and Bell Aircraft company was given access to the drawings and research on the M. 52, but the U.S. reneged on the agreement and no data was forthcoming in return . Bell's supersonic design was still using a conventional tail and they were battling the problem of control . </P> <P> They utilized the information to initiate work on the Bell X-1 . The final version of the Bell X-1 was very similar in design to the original Miles M. 52 version . Also featuring the all - moving tail, the XS - 1 was later known as the X-1 . It was in the X-1 that Chuck Yeager was credited with being the first person to break the sound barrier in level flight on October 14, 1947, flying at an altitude of 45,000 ft (13.7 km). George Welch made a plausible but officially unverified claim to have broken the sound barrier on 1 October 1947, while flying an XP - 86 Sabre . He also claimed to have repeated his supersonic flight on October 14, 1947, 30 minutes before Yeager broke the sound barrier in the Bell X-1 . Although evidence from witnesses and instruments strongly imply that Welch achieved supersonic speed, the flights were not properly monitored and are not officially recognized . The XP - 86 officially achieved supersonic speed on April 26, 1948 . </P> <P> On 14 October 1947, just under a month after the United States Air Force had been created as a separate service, the tests culminated in the first manned supersonic flight, piloted by Air Force Captain Charles "Chuck" Yeager in aircraft #46 - 062, which he had christened Glamorous Glennis . The rocket - powered aircraft was launched from the bomb bay of a specially modified B - 29 and glided to a landing on a runway . XS - 1 flight number 50 is the first one where the X-1 recorded supersonic flight, at Mach 1.06 (361 m / s, 1,299 km / h, 807.2 mph) peak speed; however, Yeager and many other personnel believe Flight #49 (also with Yeager piloting), which reached a top recorded speed of Mach 0.997 (339 m / s, 1,221 km / h), may have, in fact, exceeded Mach 1 . (The measurements were not accurate to three significant figures and no sonic boom was recorded for that flight .) </P> <P> As a result of the X-1's initial supersonic flight, the National Aeronautics Association voted its 1948 Collier Trophy to be shared by the three main participants in the program . Honored at the White House by President Harry S. Truman were Larry Bell for Bell Aircraft, Captain Yeager for piloting the flights, and John Stack for the NACA contributions . </P>

When did we break the speed of sound