<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> <P> This claim is widely disputed, even by pilots in his unit . All of the effects he reported are known to occur on the Me 262 at much lower speeds, and the ASI reading is simply not reliable in the transonic . Further, a series of tests made by Karl Doetsch at the behest of Willy Messerschmitt found that the plane became uncontrollable above Mach 0.86, and at Mach 0.9 would nose over into a dive that could not be recovered from . Post-war tests by the RAF confirmed these results, with the slight modification that the maximum speed using new instruments was found to be Mach 0.84, rather than Mach 0.86 . </P>

What happens when an airplane breaks the sound barrier