 Shortly after the Korean War, some Douglas C-54 Skymasters were converted to air-sea rescue work and redesignated SC-54, replacing all the Flying Fortresses and Super Fortresses still in service.The SC-54 sometimes carried an airborne lifeboat and could carry more rescue supplies over longer distances.In the Vietnam War, American naval vessels and aircraft from both the U.S. Navy and the U.S. Air Force participated in air-sea rescue patrols in the Gulf of Tonkin.