Boeing's liquid hydrogen-powered Phantom Eye unmanned airborne system completed its second flight Feb. 25, 2013 demonstrating capabilities that will allow it to perform intelligence, surveillance and reconnaissance (ISR) missions for up to four days without refueling. During the flight, at NASA's Dryden flight Research Center at Edwards Air Force Base, Calif., Phantom Eye climbed above an altitude of 8,000 feet and remained aloft for 66 minutes at a cruising speed of 62 knots before landing.