When planes fly faster than the speed of sound, air molecules can’t get out of the way fast enough and begin to pack together. Eventually they form a wave in front of the aircraft, creating a burst of air pressure. And you get a big bang - the sound of an aircraft breaking the sound barrier - a sonic boom. This sonic boom can damage structures and break glass. Because of this, supersonic overland flight has been banned in the United States since the 1970s. That was always a problem for aircraft like The Concorde - it simply wasn't allowed to get any further than the eastern seaboard when flying from Europe. But now, America's FAA is in the process of lifting this restriction. In this episode of Weekend One on One, William Crossley, the head of aeronautics and astronautics at Purdue University in the US, explains commercial flights traveling at supersonic speeds could reduce a cross-country flight from five hours to one hour, saving people valuable time.