Douglas DC-7 DC-7C Seven Seas

Early DC-7s were bought only by US carriers: for European airlines the small increase in range was not worth it. Douglas answered in 1956 with the DC-7C, named "Seven Seas", the programme's extended-range version.

The changes are structural. Two 5 ft (1.5 m) wing-root inserts add fuel, cut interference drag and — by moving the engines further outboard — make the cabin quieter; the optional nacelle tanks of Pan Am's and South African's DC-7Bs become standard. The fuselage, already stretched 40 inches over the DC-6B with a plug behind the wing, gains another 40-inch plug ahead of the wing for a total length of 112 ft 3 in (34.21 m). The engines are improved R-3350s of 3,400 hp (2,500 kW).

In the summer of 1956 Pan Am's DC-7C began flying the westward North Atlantic leg reliably, something achieved only occasionally until then. BOAC was forced to buy DC-7Cs rather than wait for its Bristol Britannias, and SAS used them on cross-polar routes to North America and Asia. It outsold its rival, the Lockheed L-1649A Starliner, which entered service a year later, but the arrival of the Boeing 707 and Douglas DC-8 in 1958-60 cut sales short.

Its figures, from Jane's all the World's Aircraft 1959-60: 34.21 m long, 127 ft 6 in span, 33,005 kg empty, 64,864 kg maximum take-off weight, 653 km/h top speed, 557 km/h recommended cruise, a 6,614 m ceiling at maximum gross weight and up to 5,635 miles (9,069 km) of range on maximum fuel. It carries five flight crew and four attendants, up to 105 passengers and 18,440 lb of cargo and baggage, with 7,824 US gallons in eight wing tanks. 121 were built, and the price rose from $1,155,560 (£800,000) in 1956 to $1,343,385 (£930,000) in 1958.