When the experimental XB-1 aircraft achieved supersonic speeds on a test flight, it did not create a disruptive sonic boom – thanks to a physics phenomenon called the Mach cutoff

Boomless Cruise is based on physics known as the Mach cutoff, in which a sonic boom refracts in the atmosphere and never reaches the ground. This was achieved by breaking the sound barrier at a higher altitude, with the exact speeds varying based on the atmospheric conditions.