<P> During WWII and immediately thereafter, a number of claims were made that the sound barrier had been broken in a dive . The majority of these purported events can be dismissed as instrumentation errors . The typical airspeed indicator (ASI) uses air pressure differences between two or more points on the aircraft, typically near the nose and at the side of the fuselage, to produce a speed figure . At high speed, the various compression effects that lead to the sound barrier also cause the ASI to go non-linear and produce inaccurately high or low readings, depending on the specifics of the installation . This effect became known as "Mach jump". Before the introduction of Mach meters, accurate measurements of supersonic speeds could only be made externally, normally using ground - based instruments . Many claims of supersonic speeds were found to be far below this speed when measured in this fashion . </P> <P> In 1942, Republic Aviation issued a press release stating that Lts . Harold E. Comstock and Roger Dyar had exceeded the speed of sound during test dives in the P - 47 Thunderbolt . It is widely agreed that this was due to inaccurate ASI readings . In similar tests, the North American P - 51 Mustang, a higher performance aircraft, demonstrated limits at Mach 0.85, with every flight over M0. 84 causing the aircraft to be damaged by vibration . </P> <P> One of the highest recorded instrumented Mach numbers attained for a propeller aircraft is the Mach 0.891 for a Spitfire PR XI, flown during dive tests at the Royal Aircraft Establishment, Farnborough in April 1944 . The Spitfire, a photo - reconnaissance variant, the Mark XI, fitted with an extended' rake type' multiple pitot system, was flown by Squadron Leader J.R. Tobin to this speed, corresponding to a corrected true airspeed (TAS) of 606 mph . In a subsequent flight, Squadron Leader Anthony Martindale achieved Mach 0.92, but it ended in a forced landing after over - revving damaged the engine . </P> <P> In the 1990s, Hans Guido Mutke claimed to have broken the sound barrier on 9 April 1945 in the Messerschmitt Me 262 jet aircraft . He states that his ASI pegged itself at 1,100 kilometres per hour (680 mph). Mutke reported not just transonic buffeting but the resumption of normal control once a certain speed was exceeded, then a resumption of severe buffeting once the Me 262 slowed again . He also reported engine flame out . </P>

When did the first plane break the sound barrier