Aerospace startup Boom says they've proven quiet supersonic flight is possible with their passenger airplanes after a successful second test flight.

Boom Supersonic passed a major milestone last month when its XB-1 prototype became the first civil aircraft to break the sound barrier over the continental US. Less than a month later, Chief Test Pilot Tristan “Geppetto” Brandenburg has once again surpassed Mach 1 in the experimental plane while flying as high as 36,