The Lockheed R6V Constitution began as a proposal to Pan Am for an airliner with greater range and passenger capacity than the Lockheed L-049 Constellation. Development continued during World War II under the lead of the Navy, which ordered two prototypes as R6Os. By the end of the war, Pan Am had decided that the Constitution and the Convair 37 were too big. The first flight of the XR6O-1 Constitution, BuNo 85163 was flown from Burbank to Muroc Army Air Base on November 9, 1946. The second XR6O-1, BuNo 85164 flew in June 1948. The two Constitutions served initially with VR-44 at NAS Alameda, California. When VR-44 was disestablished in 1950, the Constitutions were transferred to VR-5 at NAS Moffett.