The Ryan ST (Sport Trainer) family represents a significant shift in aviation training, moving away from the fabric-covered biplanes that dominated the early 20th century. Designed by aviation pioneer T. Claude Ryan, the ST first took flight on June 8, 1934. The aircraft was characterized by a low-wing configuration and an all-metal monocoque fuselage, featuring two open tandem cockpits for an instructor and student. While the series began as a successful line of civilian sport airplanes, it evolved into a critical military asset during World War II.
Production occurred at the Ryan Aeronautical Company facilities in San Diego, California, between 1934 and 1943. A total of 1,568 aircraft were produced across the entire ST family. This included 315 civil and early military units, followed by 1,253 military versions produced during the 1942–1943 period. The most prominent U.S. military variant, the PT-22 Recruit, served as the U.S. Army Air Corps' first purpose-built monoplane primary trainer. Depending on the source, between 1,023 and 1,048 PT-22s were accepted by the U.S. Army Air Forces to prepare pilots for modern low-wing fighters.
Technical specifications varied by model. The original civil ST used a 95 hp Menasco B-4 inverted inline piston engine, while the ST-A aerobatic version utilized a 125 hp Menasco C-4. The export STM series, used by the Netherlands East Indies, employed the 150 hp Menasco C-4S "Pirate" engine. In contrast, the PT-22 Recruit transitioned to a radial powerplant, utilizing the 160 hp Kinner R-540 series engine. Performance for the STM-S2 variant included a maximum speed of 228 km/h and a range of 560 km.
Beyond the United States, the Ryan Trainer saw diverse service. The Netherlands government in exile ordered 108 STM-2 aircraft in 1940, with 60 assigned to the Netherlands East Indies Army Air Service (KNIL-ML) and 48 to the Netherlands Naval Air Service (MLD), the latter including 24 float-equipped STM-S2s. These aircraft performed reconnaissance and coastal patrols during the Japanese advance starting December 8, 1941. Other operators included the air forces of China, Ecuador, and Mexico. In Guatemala, the aircraft were even modified as fighters by covering the front cockpit and adding armament.
Today, the Ryan Trainer is remembered as a versatile airframe that bridged the gap between basic training and combat aviation. Several examples are preserved in museums, including a PT-22A at the National Air and Space Museum and an ST-A at the San Diego Air & Space Museum. A flying STM-S2 is maintained by the Royal Australian Air Force's heritage fleet.