August 21, 2007: The U.S. Department of Defense successfully completed developing and testing flight control software for UAVs, that enables these unmanned aircraft to safely and effectively refuel in flight. The autonomous refueling systems uses GPS and inertial guidance systems, plus a video recognition system that handled the final approach in an impressive fashion. The Department of Defense is developing large UAVs designed to stay in the air for days at a time. Also, any UAV large enough to refuel in the air (Predator size and up would be stable enough in the air for this), would benefit from taking off with a larger payload (sensors or communications transponder), and staying in the air via in-flight refueling.