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 ...

Editor's note: Boom Supersonic successfully broke the sound barrier with the XB-1 today in a major milestone. Read our coverage here. Boom Supersonic plans to break the sound barrier during a test ...

During the XB-1's historic flight on Tuesday—its 12th test flight overall—the aircraft stayed supersonic for around four minutes before breaking the sound barrier two more times during the ...