. "*DC-4\n*DC-6"@en . . "Douglas DC-7"@en . . . . . . . . . . "* List of civil aircraft"@en . "*Douglas DC-7 operators"@en . "*Lockheed Constellation\n*Boeing 377"@en . . . . . . . "Pan American World Airways originally requested the DC-7 in 1945, as a civilian version of the C-74 Globemaster military transport. It cancelled its order shortly afterward. American Airlines revived the designation when it requested an extended-range DC-6 for its transcontinental services. At the time, the Lockheed Constellation was the only aircraft capable of making a non-stop coast-to-coast flight in both directions. Douglas was reluctant to build the aircraft until AA president C. R. Smith placed a firm order for twenty-five at a price of $40 million, covering Douglas's development costs."@en . . "Pan American World Airways originally requested the DC-7 in 1945, as a civilian version of the C-74 Globemaster military transport. It cancelled its order shortly afterward. American Airlines revived the designation when it requested an extended-range DC-6 for its transcontinental services. At the time, the Lockheed Constellation was the only aircraft capable of making a non-stop coast-to-coast flight in both directions. Douglas was reluctant to build the aircraft until AA president C. R. Smith placed a firm order for twenty-five at a price of $40 million, covering Douglas's development costs. The prototype flew in May 1953, and American received its first DC-7 in November, inaugurating the first non-stop coast-to-coast service in the country (taking 8 hours) and forcing rival TWA to offer a similar service with its Super Constellations. Both aircraft, however, suffered from unreliable engines, and many transcontinental flights had to be diverted because of in-flight engine failures. The original DC-7 was followed by another variant the DC-7B, which was identical except for increased fuel capacity in extended engine nacelles, which extended the flight range. The early DC-7s were only sold to U.S. carriers. European carriers could not take advantage of the small range increase in the early DC-7, so Douglas released an extended-range variant, the DC-7C (Seven Seas) in 1956. A 10 ft (3.05 m) wing-root insert added fuel capacity, reduced induced drag, and made the cabin quieter by moving the engines further outboard. The fuselage, which had been extended over the DC-6B's by a 40in (1.02 m) plug behind the wing for the DC-7 and -7B, was lengthened by a similar plug ahead of the wing to give the DC-7C a total length of 112 ft 3 in (34.21 m). Pan Am used DC-7C aircraft to inaugurate the first non-stop New York-London service, forcing BOAC to buy the aircraft rather than wait on the delivery of the Bristol Britannia. The DC-7C found its way into several other overseas airlines' fleets, including SAS, which used them for cross-polar service to North America and Asia. However, -7C sales were cut short by the arrival of the Boeing 707 and DC-8 a few years later, when they took over on the coast-to-coast services. Starting in 1959, Douglas began converting DC-7A and DC-7C aircraft into DC-7F freighters, which extended the life of the aircraft past its viability as a passenger transport."@en .