The 3rd Air Force was constituted as Southeast Air District on October 19, 1940 and activated on December 18, 1940. It was redesignated 3rd AF in early 1941.
The 3rd AF trained units and crews for bombardment, fighter, and reconnaissance operations. 3rd AF was engaged in antisubmarine activities from December 1941 to October 1942. During 1940-1941 the 3rd AF also had some continental air defense assignments.