In April 1949, United, American, Delta, National, and Braniff were flying DC-6s in the United States. United flew them to Hawaii, Braniff flew them to Rio de Janeiro, and Panagra flew Miami-Buenos Aires; KLM,
SAS, and Sabena flew DC-6s across the Atlantic.
BCPA DC-6s flew Sydney to Vancouver, and
Philippine flew Manila to London and Manila to San Francisco.
Pan Am used DC-6Bs to start transatlantic tourist-class flights in 1952. These were the first DC-6Bs that could gross , with CB-17 engines rated at on 108/135 octane fuel. Several European airlines followed with transatlantic services. The DC-6B and C subtypes could often fly nonstop from the eastern US to Europe but needed to refuel in Goose Bay, Labrador, or Gander, Newfoundland, when flying westbound into prevailing westerly winds. Douglas designed four variants of the DC-6: the basic DC-6, and the longer-fuselage () higher-gross-weight, longer-range versions—the DC-6A with cargo doors forward and aft of the wing on the left side, with a cargo floor; the DC-6B for passenger work, with passenger doors only and a lighter floor; and the DC-6C convertible, with the two cargo doors and removable passenger seats. The DC-6B, originally powered by
Double Wasp engines with Hamilton Standard 43E60 constant-speed reversing propellers, was regarded as the ultimate piston-engine airliner from the standpoint of ruggedness, reliability, economical operation, and handling qualities. Similar to the DC-6A, the military version was the USAF C-118 Liftmaster; the USN R6D version used the more powerful R-2800-CB-17 engines. These were later used on the commercial DC-6B to allow international flights. The R6D Navy version (in the late 1950s and early 1960s) had Curtiss Electric constant-speed reversing propellers. The USAF and USN renewed their interest in the DC-6 during the
Korean War and ordered 167 C-118/R6D aircraft, some of which later found their way to civil airlines.
Harry Truman's first presidential aircraft was an Air Force short-fuselage DC-6 which was designated
VC-118, and named
The Independence. It is preserved in the
National Museum of the United States Air Force at
Dayton, Ohio. Total production of the DC-6 series was 704, including military versions. In the 1960s two DC-6s were used as transmitter platforms for educational television, based at
Purdue University, in a program called the
Midwest Program on Airborne Television Instruction. Many older DC-6s were replaced in airline passenger service from the mid-1950s by the
Douglas DC-7, but the simpler, more economical engines in the DC-6 have meant the type has outlived the DC-7, particularly for cargo operations. DC-6/7s surviving into the jet age were replaced in frontline intercontinental passenger service by the
Boeing 707 and
Douglas DC-8. Basic prices of a new DC-6 in 1946–47 were around £210,000–£230,000 and had risen to £310,000 by 1951. By 1960, used prices were around £175,000 per aircraft. Prices for the DC-6A in 1957–58 were £460,000–£480,000. By 1960, used prices were around £296,000. ==Variants==