Lineage. Constituted as 4 Pursuit Squadron (Interceptor) on 20 Nov 1940. Activated on 15 Jan 1941. Redesignated as: 4 Fighter Squadron on 15 May 1942; 4 Fighter Squadron, Single Engine, on 20 Aug 1943. Inactivated on 7 Nov 1945. Redesignated as 4 Fighter Squadron (All Weather) on 19 Dec 1946.