More than 20 years since the final Concorde flight, is a small US start-up now on course to bring back supersonic air travel? TIM ROBINSON FRAeS and JOE COLES debrief Boom’s XB-1 test pilot and consider the next steps in civil supersonics.

Boom Supersonic’s XB-1 creates a sonic boom inaudible from the ground below when flying at the exact right speed and altitude.

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,

The scaled-down prototype, nicknamed the "Baby Boom", broke the sound barrier for the first time during a test flight over the Mojave Desert in California in late January. The small jet, officially called XB-1, reached an altitude of 35,000 feet before accelerating to Mach 1.1 (844mph) – "10% faster than the speed of sound", said Sky News.

If you've been keeping tabs on aviation news as of late, you saw that Boom Supersonic just recently broke the sound barrier with its XB-1 demonstrator aircraft. Oddly enough, no one on the ground heard a thing during its "boomless" cruise.

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