Photos: Unmanned vehicles take to air, land and sea

At the high end of the Air Force's drone fleet is the Global Hawk, which, according to the Air Force, can travel a range of 12,000 nautical miles, climb up to 65,000 feet and fly at speeds approaching 340 knots (about 400 mph) for as long as 35 hours. Used primarily for surveillance, the first seven production aircraft are flying daily missions in the Iraq war, said Lt. Gen. Hoffman. They've also experimented with outfitting the drone with a terabyte server capable of storing data gleaned from missions and beaming it through a local area network to users on the ground with radios. But one lingering challenge with existing UAVs and the Global Hawk in particular is that they're not exactly "plug and play," Hoffman said. Translation: "Any change you want to make there involves major surgery to the central nervous system."