The L-21 was a U.S. Army Korean war era light liaison aircraft that later was used by the USAF. Prototypes were delivered in 1951 (as the YL-21) with the L-21A produced starting in 1952. The L-21B was redesignated as the U-7A in 1962.
The L-21 is a single engine, high-wing, 2-seater aircraft, based on the Piper PA-18, often used for agricultural purposes in the civilian market. The U.S. Air Force used the PA-18 in civil markings for contract training at civilian schools.
Piper L-21A Super Cub at the Texas Military Forces Museum, Camp Mabry, TX, 3 February 2006. Photo courtesy of Bob Pettit.