Unit designations of the United States Army Air Force and United States Air Force

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).

Unit numbers were as high as 5908 (San Bernardino's AAF BU on 1 April 1944), and at least two AAF BUs included smaller organizations, e.g., the 85 AAF BU had Langley's Section A, Spokane's Sec E, McClellan's Sec C, & San Bernardio's Sec D; and Elmendorf's 87 AAF BU Sec A & E. AAFBU designations were used for base operating units (e.g., Dover's "312th Air Base and HQ Sq” was replaced on 10 April 1944 by the “125th Base Unit”, which was redesignated “125th AAF Base Unit” on 15 September 1944), but the unit designation was also used for other missions such as:
 * exhibition (e.g., Wright-Patt's "3100 USAF Exhibition Unit"),
 * flight testing (Muroc’s “730 AAF BU” had several redesignations through 2759th Experimental Wing)
 * history (Elmendorf's "1 Historical Unit"),
 * intelligence (Elmendorf's "2 Counter Intelligence Unit"),
 * inspection/investigations (Langley's "1001 IG Unit", Bolling's 11 AF BU became the "1005 IG Sp Investigations Unit"),
 * logistics (Hickam's "Phase-Out Unit, Pacific Air Cmnd", Hill's "7 Dep Unit", Kelly's 44 "Stat Svcs Unit"),
 * photography (Bolling's "16 Domestic Photographic Unit" and "Combat Camera" Units, Colorado Springs' "HQ PROTU", & Wright-Patt's "6 Photographic Technical Unit"),
 * publications (Scott's "3310 Fld Printing Unit"),
 * radar/radio/electronics (Andrews' 263 AAFBU, Eglin's "1 Proving Comd Elect Unit", Elmendorf's "Flt Con Unit", Kelly's "MATS Teletype Unit", March's "3 Shoran Beacon Unit", MacDill's "1 Computer Tech Unit", McChord's "11 Radar Calibration Unit", McGuire's "2 AAF Elect Exper Unit", Rome/Langley "7 Radar Calibration Unit", Robins' "1 Radar & VHF Installation & Maint Unit"),
 * search & rescue (Hickam's "7 Search & Rscu Unit", Lowry's "9 Rscu Unit"),
 * services/support (Elmendorf's "AAB Svc Unit", Hickam's "Test Svc Unit"),
 * training (Bunker Hill's "Basic Mil Tng Unit, Prov", Homestead's "2 Opl Tng Unit", MacDill's "3 Engrg Avn Unit Tng Cen" & "17 Alt Tng Unit", March's "Air Orientation Unit", Mountain Home's "6 Alt Tng Unit", Shaw's "Sp Tng Unit", Tyndall's "25 Alt Tng Unit", Westover's "2 Alt Tng Unit"),
 * weapons testing (Wendover's Special Weapons Field Test Unit), and
 * weather (Tinker's “Air Task Wea Recon Unit”).

Cold War unit designations
Most AAFBUs were inactivated before the 1947 USAF was established, but some were redesignated Air Force Base Units (AF BU), e.g., base operating units on 26 September 1947 such as Brooks' 306th, Barksdale's 2621st, and Williams' 3010th. Although many base units were smaller than squadrons, some AF BUs included squadrons, e.g., the E and R Squadrons of Bolling's 4 AF BU, and Sq R (Bergstrom) and Sq M (Offutt) of the 130 AF BU. New AF BU unit designations were established as late as 16 May 1948 (Williams' 775 AF BU), and the 496 Finance Disbursing Unit at Kelly was designated on 19 February 1951. Nearly all "unit" designation were obsolete c. 1 May 1952 when MacDill's "2156 Air Rscu Unit" was inactivated.