The 420th Flight Test Squadron is an active United States Air Force squadron. The squadron was first activated as the 420th Night Fighter Squadron, one of the first dedicated night fighter operational training squadrons of the Air Force. It trained replacement night fighter pilots who were then deployed overseas into combat until its inactivation in March 1944 due to a re-alignment of training unit designations. The squadron was reactivated on 4 October 2019 to support flight testing of the Northrop Grumman B-21 Raider.