Mach 1 refers to the speed of sound in air at sea level, which is approximately 343 meters per second (1,125 feet per second) or about 1,235 kilometers per hour (767 miles per hour). The exact speed can vary based on factors like temperature and altitude. When an object travels at Mach 1, it creates a shock wave, which is often heard as a sonic boom. In aviation and aerospace, reaching Mach 1 is a significant milestone for aircraft and spacecraft. Supersonic flight, which occurs at speeds greater than Mach 1, allows for faster travel and has been achieved by various military jets and experimental aircraft, such as the Concorde and the X-15.