Douglas DC-7 American Airlines. Douglas' largest and last piston engined airliner, the DC-7 was one of the first airliners capable of nonstop trans Atlantic crossings between New York and London.
Previously the DC-7 designation had applied to a commercial development of the C74 Globemaster I that PanAm had ordered. As it emerged though the DC-7 arose from an American Airlines requirement for a stretched longer range development of the DC-6. The resulting aircraft was based on the same wing of the DC-6 (also the same basic wing designed for the DC-4), with a stretched DC-6 fuselage, more powerful Wright Turbo Compound engines and extra fuel allowing Douglas to guarantee it could offer nonstop transcontinental US range in both directions.