Boom Supersonic's XB-1 demonstrator jet became the first U.S.-made civilian supersonic jet to break the sound barrier. The independently funded XB-1 reached a speed of Mach 1.122, or about 750 mph ...

The sound barrier is something many people have heard of, but few understand, as it's somewhat of a misnomer. The speed of sound is known as Mach 1 (767 mph), and when an object moves beyond this ...