The Sea Serpent, a modified Boeing 747 aircraft, taxis out of Pan Am hangar 19 as another Boeing 747 stands in the foreground. The aircraft are undergoing modification as part of a Military Airlift Command plan to use 115 Boeing and McDonnell Douglas jetliners as air ambulances in the event of war. The aircraft, which would be part of the Civil Reserve Air Fleet, would airlift patients back to the United States