How fast is a plane going if it is traveling at mach 1?

Mach 1 is the speed of sound in air, which varies based on temperature and altitude but is approximately 343 meters per second (about 1,125 feet per second) at sea level and at 20 degrees Celsius (68 degrees Fahrenheit). Therefore, if a plane is traveling at Mach 1, it is moving at around 1,225 kilometers per hour (about 761 miles per hour) under these conditions. This speed can change with different atmospheric conditions.