The Boeing X-37, also known as the Orbital Test Vehicle (OTV), is a reusable unmanned spacecraft. It is boosted into space by a launch vehicle, then re-enters Earth's atmosphere and lands as a spaceplane. The X-37 is operated by the United States Air Force for orbital spaceflight missions intended to demonstrate reusable space technologies. It is a 120%-scaled derivative of the earlier Boeing X-40.The X-37 began as a NASA project in 1999, before being transferred to the U.S.