Supersonic planes travel faster than the speed of sound.
The speed of sound is about 1220 km/h at sea level at 15°C.
Sound travels slower higher up, so the speed of sound is about 1060 km/h at 12,000 m.
Supersonic plane speeds are given in Mach numbers. These are the speed of the plane divided by the speed of sound at the plane’s altitude.
A plane flying at 1500 km/h at 12,000 m, where the speed of sound is 1060 km/h, is at Mach 1.46.
A plane flying at supersonic speeds builds up shock waves in front and behind because it keeps catching up and compressing the sound waves in front of it. Energy, force and motion
In 1947 Chuck Yeager of the USAF made the first supersonic flight in the Bell X-1 rocket plane. The X-15 rocket plane later reached speeds faster than Mach 6. Speeds faster than Mach 5 are called hypersonic.
The first jet plane to fly supersonic was the F-100 Super Sabre fighter of 1953. The first supersonic bomber was the USAF’s Convair B-58 Hustler, which was first used in 1956.
Supersonic jet fighter planes are used by the military to intercept and attack enemy aircraft.
Spaceplanes of the near future may reach speeds of Mach 15.
The double shock waves create a sharp crack called a sonic boom that is heard on the ground. Two booms can often be heard one or two seconds apart.
In 1976 Concorde became the first supersonic aircraft to carry passengers on commercial flights. It was retired from service in 2003.