Vertical takeoff, horizontal landing (VTHL) is the mode of operation for all current and formerly operational orbital spaceplanes, such as the Boeing X-37, the NASA Space Shuttle, the 1988 Soviet Buran space shuttle, as well as the circa-1960 USAF Boeing X-20 Dyna-Soar project. For launch vehicles an advantage of VTHL over HTHL is that the wing can be smaller, since it only has to carry the landing weight of the vehicle, rather than the takeoff weight.[11]