Douglas DC-4 C-54M

The C-54M was not a production version of the Skymaster but a field modification born of one specific logistical emergency: the Soviet blockade of Berlin. When the Soviet Union cut the land routes into the western sectors of the city in 1948, the Allies had to supply the city's population entirely by air, and coal was an essential part of that tonnage. C-54s and Navy R5Ds, more than 300 aircraft in all, formed the backbone of the United States contribution to the airlift, and to squeeze the maximum payload out of a shuttle service between the bases in western Germany and airfields such as Tempelhof it was decided to lighten a batch of airframes as far as possible.

The chosen basis was the C-54E, the sub-series that had introduced a further revision of the fuel tanks and provision for rapid conversion from passenger to cargo configuration, of which Douglas had built 125. Thirty-eight of them were turned into coal carriers under the designation C-54M: the supplementary fuel tanks, unnecessary on such short legs, were removed, along with every item of interior fitting that contributed nothing to the mission (linings, passenger equipment and other amenities), so that each kilogram saved in empty weight became coal on board. The result was an aircraft with a bare hold devoted to a single commodity. Berliners nicknamed the procession of Skymasters the "Rosinenbomber" (raisin bombers) after the small parachutes of sweets that some crews dropped to children beneath the approach path; the coal-laden C-54Ms were part of that same unbroken stream of landings.

The figure of 38 conversions is the one given by the reference variant lists (English Wikipedia, "List of Douglas C-54 Skymaster variants", and the Tinker depot historical profile published by DVIDS, which describes the removal of tanks and amenities). German Wikipedia, however, states in the body of its article that 27 C-54Es were converted to C-54M, while repeating the figure of 38 in its own variant table; this entry keeps the 38 of the principal sources and records the discrepancy.

The letter "M" was reused shortly afterwards for a modification of a very different kind. With the Korean War, which began in 1950, the C-54 became the main aircraft of the trans-Pacific airlift, and aeromedical evacuation capacity was needed: 30 C-54Es were converted into air ambulances under the designation MC-54M, fitted to carry litters and medical staff. A single MC-54M was later converted again into a VIP transport as the VC-54M. According to German Wikipedia, during the 1960s the USAF converted a total of 15 Skymasters into VIP transports (four C-54Ds, eight C-54Es, two C-54Gs and one C-54M), which matches that airframe.

The later operational life of the C-54Ms and MC-54Ms was that of any second-line Skymaster, with two documented losses in the autumn of 1955. On 17 November 1955 MC-54M 44-9068 struck Mount Charleston, Nevada, with 14 people on board and no survivors: the aircraft was carrying scientific and technical personnel from the Lockheed Skunk Works to Area 51 to work on the U-2 programme, was flying out of contact with air traffic control for reasons of secrecy, and an attempt to shorten the route by ten minutes, combined with a storm front that blew it off course and an error in the assumed position relative to the Spring Mountain range, ended in the impact. Less than a month later, on 11 December 1955, C-54M 44-9094 struck a mountain near Ketama, Morocco, killing all eight on board. The USAF went on operating Skymasters until 1972, by then replaced on the main routes by the C-124 Globemaster II.

Of the 38 C-54Ms a single one survives: 44-9030, a Berlin Airlift veteran, on static display at the Air Mobility Command Museum in Dover, Delaware, which presents it as the last C-54M in existence. It is thereby one of the few material witnesses to the campaign that turned the Skymaster into a symbol of the Cold War.