The 5th Air Force was constituted as the Philippine Department AF on August 16, 1941 and activated in the Philippines on September 20, 1941. It was re-designated Far East AF in October of 1941, and became the 5th AF in February 1942.
The 5th AF participated in the defense of the Philippines after Pearl Harbor. Netherlands Indies. The 5th AF participated in operations in Papua, New Guinea, Netherlands East Indies, and the liberation of the Philippines.