An Air Force Flight Test Center B-52H Stratofortress performs a captive carry flight of the X-51A WaveRider over Edwards Air Force Base, Calif. on Dec. 9, 2009. The captive carry mission is a key test milestone to ready to light the X-51's scramjet engine during the vehicle's first powered hypersonic flight in early 2010. (U.S. Air Force photo/Mike Cassidy)