|Eastern Airlines DC-2.|
https://en.wikipedia.org/wiki/Washington-Hoover_Airport. That would date my dad's pictures to late-1941, which is possible because I read in one of his 1941 diary entries that he was thinking of buying a 35mm format camera. He bought an American-made Perfex camera, made by the Candid Camera Corporation of Chicago. I assume this roll of film was one of his early tests. The Cameraquest web page describes the Perfex cameras if you are interested.
When it opened, National Airport was considered the “last word” in airports – a concentration of the ultramodern developments in design of buildings, handling of planes, air traffic and field traffic control, field lighting, facilities for public comfort and convenience, and surface vehicle traffic control.Well, not quite. Across the ocean, in Berlin, the spectacular Templehof Airport was under construction and almost complete in 1941. Please see my 2016 article on Templehof.