The 166th was upgraded with new F-84F Thunderstreaks in November 1957, the gaining command of the squadron became Tactical Air Command (TAC), however, it remained attached to Air Defense Command in a secondary role. In 1959, the need for active duty Air Defense Command bases and regular Air Force fighter-interceptor operations were diminishing and the intent to scale back operations at Youngstown AFB was announced on 28 October 1959. The Ohio Air National Guard moved the 121st FBG back to Lockbourne Air Force Base on 1 March 1960.