During World War II, the armed forces of many countries used the C-47 and modified DC-3s for the transport of troops, cargo, and wounded. The US Navy designation was R4D. More than 10,000 aircraft were produced in
Long Beach and
Santa Monica, California, and
Oklahoma City, Oklahoma. Between March 1943 and August 1945, the Oklahoma City plant produced 5,354 C-47s.
Super DC-3 Large numbers of DC-3s and surplus C-47s were in commercial use in the 1940s. In response to proposed changes to the
Civil Air Regulations airworthiness requirements that would restrict use of these aircraft, Douglas offered a conversion to improve takeoff and single-engine performance. The fuselage of the DC-3S or "Super DC-3", was strengthened and lengthened by ahead of the wings. The wing center section remained the same but the outer wing panels had a 4
° trailing edge sweep and squared-off wingtips that reduced the wingspan by . There was also a new square tail fin with a large dorsal fillet that was taller than the DC-3's to compensate for the increased torque from more powerful engines. Either
Wright R-1820-80 Cyclones or
Pratt & Whitney R-2000 Twin Wasps with short, jet ejection-type exhaust stacks could be fitted. The DC-3S made its first flight on 23 June 1949. The changes met the new FAR 4B airworthiness requirements and 38 passengers could be carried, with increased speed to compete with newer airliners. Douglas offered to convert existing aircraft for $150,000 per aircraft, however little interest was expressed by commercial operators. The empty and loaded weight of the R4D-8 increased but so did top speed and cruise speed . Fuel capacity also doubled to and despite doubling the fuel capacity range was only increased to . ==Operational history==