0.85 at 35,000 ft altitudeThe official  land speed record 341.11119.11227.98763The  speed of sound  in dry air at sea-level pressure and 20 °C34311251235768 Mach  1 by definition. 20 °C = 293  kelvin . Muzzle velocity  of an  AK47   assault rifle   bullet 7102,3302,6001600Official  flight airspeed record 9803,2153,5302,194 Space