But while the successful test flight of XB-1 shows that supersonic flight without sonic booms is technically feasible, the next phase is making it economically feasible. Right now, both subsonic and sonic boom-producing supersonic travel are cheaper than using this Mach cutoff method.

US aeronautics agency NASA managed to capture the Boom Supersonic XB-1 research aircraft as it broke the sound barrier during its final flight on 10 February. The flight - the XB-1's second in excess of Mach 1 - was the last in a series of test sorties by the aircraft,