The American Lockheed XFV (sometimes referred to as the Salmon) was an experimental tail-sitter prototype aircraft built by Lockheed in the early 1950s to demonstrate the operation of a vertical takeoff and landing fighter for protecting convoys. The XFV-1 was able to make a few transitions in flight from the conventional to the vertical flight mode and back, and had briefly held in hover at altitude. Performance remained limited by the confines of the flight test regime. With the realization that the XFV's top speeds would be eclipsed by contemporary fighters and that only highly-experienced pilots could fly the aircraft, the project was cancelled in June 1955.