The Fw 200 resulted from a proposal by Kurt Tank of Focke-Wulf to Dr. Rudolf Stuessel of Deutsche Lufthansa to develop a landplane to carry passengers across the Atlantic Ocean to the US. At the time, it was an unusual concept because airlines used seaplanes on long over-water routes. To fly long distances economically, the Fw 200 was designed to cruise at an altitude of over - as high as possible without a pressurized cabin. Existing airliners were designed to cruise at altitudes below 1,500 m (5,000 ft). The Fw 200 was briefly the world's most modern airliner, until other high-altitude airliners started operating: the Boeing 307 in 1940 and the Douglas DC-4 in 1942. The designation "Condor" was chosen because, like the condor bird, the Fw 200 had a very long wingspan relative to other planes of its era, to facilitate then high-altitude flight.