While the plane’s engines were still audible on the ground, surpassing the Mach cutoff ensured no one heard a disruptive sonic boom. According to the company’s February 10th announcement ...

and the company did it with no audible sonic booms on the ground. The Boom Supersonic XB-1 (pictured here in an earlier flight) flew Mach 1.122 in Boomless Cruise ... no one on the ground could ...