Hypersonic speed
In aerodynamics, hypersonic speeds are speeds that are significantly faster than the speed of sound. Any speed faster than Mach 5 (five times faster than the speed of sound; 1,715 m/s at sea level) is said to be hypersonic.  Hypersonic speeds are distinguished from supersonic speeds, because air and aircraft act very strangely at hypersonic speeds; even stranger than at supersonic speeds.