The Douglas DC-7C "Seven Seas", together with the Constellation, was the last airliner to be produced with piston engines. It was designed to meet the requirements of Pan American for use non-stop on the transatlantic routes. With 62 passengers and a maximum range of 9,076 km, the DC-7C was the best equipped for this task. It made its first flight on 20th December 1955. The DC-7C was based on the DC-7B. Its range enabled the SAS, for example, to overfly the North Pole for the first time on a route from Copenhagen to Tokyo in just 30 hours on 24th February 1957. The first DC-7C built for Pan American was delivered on 5th November 1956. Altogether 121 DC-7Cs were built.