The unmanned test run for a hypersonic jet that promised futuristic air travel between New York and London in under 45 minutes has ended in failure. The U.S. Air Force said the aircraft dropped as planned from a B-52 Bomber off the coast of Southern California only to lose control and crash into the Pacific Ocean. The X-51 was airborne for around 15 seconds before it fell out of the sky. It is still unclear what malfunctioned, but the X-51 WaveRider was supposed to be powered by a solid-rocket booster before igniting a scramjet engine and traveling six times the speed of sound. "All our data showed we had created the right conditions for engine ignition and we were very hopeful to meet our test objectives," Charlie Brink of the Air Force Research Laboratory at the Wright-Patterson Air Force Base in Ohio, said in a statement.