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.

Boom Supersonic, the American company building what promises to be the world’s fastest airliner, broke the sound barrier for its first time with a test flight in Mojave, California, on Tuesday.