The O-46, which entered service in 1936, was overtaken by the need for observation aircraft to be nimble, small and able to use rudimentary airfields. The O-46 was a large, lumbering aircraft that would have been a sitting duck for fighters. A few were in the Philippines at the start of the Pacific war in 1941 but mostly they were US based with the Air National Guard or on mundane utility work. Photo by: Rudy Arnold / Smithsonian Institution