Denver-based Boom Technology's XB-1 demonstrator plane hit Mach 1.122 — 750 mph. It's the first independently developed supersonic jet. The company is also working on a supersonic passenger airliner.
The XB-1 demonstrator has broken the speed of sound, hitting Mach 1.1. It is the first civil supersonic aircraft in US history and the first to do so since Concorde was retired in 2003. That was an ...