The Lockheed C-5 Galaxy project began in 1961, in an effort to create a heavy jet transport that would replace the Douglas C-133 Cargomaster and complement the Lockheed C-141 Starlifters. The result was an aircraft with a maximum payload of 118 tons and can carry it to a range of 5,526 km. The range can be extended by in-flight refueling. However during wartime a maximum payload of 132 t is allowed.