The Bell X-5 is a U.S. civilian experimental aircraft built by Bell Helicopter and the United States Army. It was designed to be the world's first fully autonomous VTOL vehicle, capable of vertical takeoffs and landings with no need for a pilot.
It was also the world's lightest helicopter with a fully-articulated main rotor assembly. The X-5 made its first flight on December 18, 1997, and its final flight occurred on October 12, 2007. The X-5 program was terminated in 2008 as the Army no longer required an autonomous vehicle due to greater emphasis being placed on manned helicopters. The X-5 is known as "The Swing Wing King" because it was the first fully autonomous VTOL craft to successfully complete a public demonstration flight (a swing-wing aircraft like the X-5 can take off vertically like a helicopter does but then fly forward like an airplane). The X-5 also holds the record of being the first helicopter to fly from one coast to another without refueling at sea (the previous record was five hours).