R4D-8 / C-117 Skytrain

After World War II, the US Navy modifed 100 R4Ds to Super DC-3 standards. The US Navy had 100 R4D-5s and R4D-6s converted to "Super Three" (R4D-8) standards, though other engines were used: Wright R-1820-80s. This aircraft, designated the R4D-8 had more powerful engines, newly designed wings, an enlarged tail and added landing gear doors. The name "Skytrain II" did not stick much, "Super DC-3" or "Super Three" did. The R4D-8 was designated the C-117 after 1962.

After World War II Douglas decided to modernise the DC-3, with more power and capable of carrying a greater load. This led to the Super DC-3, or DC-3S, which was issued Approved Type Certificate on 24 July 1950. Douglas put Wright 1820-C9HE engines on the prototype and initial production models. The maximum speed increased from 230 mph to 270 mph, and cruising speed increased from 207 mph to 251 mph. Although the DC-3S looked like a DC-3 (or C-47), it was much improved. The Super DC-3 had newly designed wings, an enlarged tail and landing gear doors were added. Also the nose was changed and the wings had square cut tips. It seated up to 37 passengers and it was 60 percent a completely new airplane.

This post-war development of the famous Douglas twin-engined transport was meant to replace the DC-3 in both military as well as the commercial marktes, but failed commercially due to the many military surplus C-47s flooding the market and the competition on the Convair Liner series with pressurised cabins. The conversion price was between $250,000 and $300,000, while a Convair CV340 would seat 44 passengers, flew faster and would cost about usd $570,000 brand new.

The successes of early Marine transport aircraft, especially during World War II, paved the way for what was to evolve into the modern day operational support airlift (OSA) mission. Early transports were essentially commercial aircraft, with minor modifications, that were put into military service to provide logistical support directly to the warfighter. Mostly, these aircraft had no armament or special equipment for protection during combat. Employing them in a hostile environment emerged from a warfighting necessity because no other Marine aircraft had the required payload, range, and reliability offered by these early transports.

Marine aircraft were first used in their OSA role during the late 1960s and early 1970s. OSA aircraft, mostly old C-117 "Hummers" once used during combat resupply missions in Southeast Asia, were attached to Marine Corps air stations (MCASs) at Cherry Point, NC; Yuma, AZ; Futenma, Okinawa; and Iwakuni, Japan. By the early 1980s newer, more modern OSA aircraft were entering the Marine Corps' fleet.

On 12 July 1976, the Navy phased out the last C-117 (Douglas DC-3), perhaps the most famous transport plane of all time. The last C-117 was flown from Pensacola to Davis Mountan Air Force Base, Arizona, the boneyard for obsolete military aircraft.