Any speed over the speed of sound, which is approximately 343 m/s or 761 mph or 1,225 km/h at sea level, is said to be supersonic. Many modern fighter aircraft are supersonic. The Concorde was a supersonic passenger aircraft, but, since its final retirement flight on November 26 2003, there is no supersonic passenger aircraft in service. Speeds greater than 5 times the speed of sound are sometimes referred to as hypersonic.

Chuck Yeager was the first man to break the sound barrier in level flight on October 14 1947, flying the experimental Bell X-1 at Mach 1 at an altitude of 45,000 feet (13.7 km).

A team led by Richard Noble and driver Andy Green became the first to break the sound barrier in a land vehicle October 15 1997, almost exactly 50 years after Yeager's flight.

Hans Guido Mutke claimed to have broken the sound barrier before Yeager, on April 9 1945 in a Messerschmitt Me 262. However, this claim is disputed by most experts and lacks a scientific foundation.

See also

• Sound barrier
• Mach number

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