AAF Training Film Preparation Units, Army Air Force Base Units, Air Rescue Units, Air Transport Units (later Strategic Support Units), Aircraft Warning Units, Fighter Control Units, Finance Disbursing Units, Mobile Training Units, Operational Training Units, Photographic Technical Units, Signal Equipment Installation Units, Statistical Control Units, and other air force "unit" designations of the United States began as early as 19 April 1941 when the Training Film Field Unit was activated at Wright Field (cf. 1942 First Motion Picture Unit).