The C-45 was developed from the Beech Model 18 civil transport, which first flew on 15 January 1937. The USAAF placed orders for its first aircraft in 1940 and acquired nearly 1300 modified Beech 18s for various missions, including light transport as the UC/C-45, navigation, bombing, and gunnery training as the AT-11, photo survey as the F-2, and naval service in the JRB series. In the early 1950s, 900 surviving USAF AT-11s and C-45s were rebuilt into C-45Hs, and the last aircraft was retired in 1963. AT-11s and C-45s served with various McChord-assigned units from the early 1940s through the early 1960s.