US airline 'United' has announced plans to buy 15 new supersonic airliners and return to supersonic speeds to aviation in the year 2029. <br />''<br />''Supersonic passenger flights ended in 2003 when Air France and British Airways retired Concorde.<br />''<br />''The new 'Overture' aircraft will be produced by a Denver-based company called Boom, which has yet to flight-test a supersonic jet.<br />''United's deal is conditional on the new aircraft meeting safety standards.<br />''<span style="color: #222222;"><br />''Supersonic flight is when an aircraft travels faster than the speed of sound. A typical passenger jet may cruise at about 900 kilometres per hour, but Overture is expected to reach speeds of 1,805 kilometres per hour.</span><br />