Over 10,000 Stearman trainers were built by Boeing's Wichita Division, which had purchased the Stearman Company in the late 1930s. These Kaydets, along with Fairchilds and Ryans, served as the backbone of U.S. Army and Navy primary training in World War II. The original U.S. Army Kaydet was the PT-13 with a 220 Lycoming R-680 engine. The only complete standardization of an Army and Navy production design aircraft during World War II was achieved with the Boeing-Stearman E-75, which served the Army as the PT-13D and the Navy as the N2S-5.This Kaydet was accepted by the Navy on December 7, 1943, exactly two years after the attack on Pearl Harbor. The airplane was flown to the Ottumwa, Iowa, Naval Air Station, where it was used to train naval aviation cadets until 1946.