Primary trainers represented the first of three stages of military flight training--primary, basic, and advanced. Prior to 1939, the Air Corps relied entirely on biplanes as primary trainers, but in 1940 it ordered a small number of Ryan low-wing civilian trainers and designated them as PT-16s. They were so successful that the Air Corps then ordered large numbers of improved versions, among them the PT-22. By the time production was completed in 1942, 1,023 PT-22s had been delivered. Twenty-five additional trainers, ordered for the Netherlands, were taken over by the Air Corps in 1942 and designated as PT-22As.