The Douglas DC-3, which made air travel popular and airline profits possible. The DC-3 was not only comfortable and reliable, it also made air transportation profitable. American's C.R. Smith said the DC-3 was the first airplane that could make money just by hauling passengers, without relying on government subsidies. As a result, by 1939, more than 90 percent of the nation's airline passengers were flying on DC-2s and DC-3s.