Cover Designations for Classified USAF Aircraft

Copyright © 2004-2023 Andreas Parsch

Background

In the late 1960s the U.S. Air Force began to acquire Soviet fighter aircraft for the purpose of evaluation and air-to-air combat training. The acquistion and use of these aircraft was then highly secret, and operations were flown from the test facility at Groom Lake, Nevada (a.k.a. "Area 51"). The aircraft types flown included the MiG-17 and MiG-21 initially, and later also other MiGs (e.g. MiG-23) and presumably some Sukhoi types.

Just like any other USAF pilots, the men flying the secret aircraft had to log their flight hours in standard USAF forms (specifically, the "Form 5" flight records). These forms required the entry of the aircraft type flown, but of course you couldn't simply write "MiG-21" into that line! At some time early in the HAVE DOUGHNUT program (which evaluated the USAF's first MiG-21), someone had the idea to use "fake" cover designations, which looked like ordinary Air Force designations, but which were not used by any actual aircraft. It was decided to continue the old F-for-Fighter series of the USAF, which had reached F-111, but had been discontinued in 1962 when the DOD introduced a new joint designation system. Therefore, the numbers used were 110 (the original F-110A designation had been replaced by F-4C, so that -110B, -110C etc. were de facto unused), 112, 113, etc. All designations were prefixed by a "Y", indicating a test model. Over the years, the system of assigning YF-1xx designations was extended to U.S.-built secret aircraft as well.

Originally, the designations' suffix letters were not only used to designate different versions of the same basic aircraft type (as in standard USAF designations), but also to distinguish between individual aircraft of the same type (e.g. YF-113A, YF-113C and YF-114C were all MiG-17Fs). When the USAF's Form 5 was amended to allow the entry of the tail number of the aircraft flown, use of suffix letters was reportedly changed to the more conventional "one suffix per subtype".

Other than for standard designations, the numbers and suffix letters were not allocated in sequence, but more randomly. It was also not uncommon to use one number for several basic aircraft types, see e.g. 113 and 117 in the listing below. Finally, the "F" or "YF" prefix doesn't mean "Fighter" as in normal designations (at least not anymore). Evidence for this is the TACIT BLUE demonstrator, which had a YF designation, but wasn't designed in any way to be a fighter. All said, it makes sense to hide the number of secret projects, as well as the mission or type of a certain project, by simply assigning the same designation prefix and a non-sequential numbers to all aircraft.

From the time frame of the YF-113G, it is clear that the system was still in use in the mid-1990s. It is not known what kind of "cover designations" are used nowadays, but the leaked designations YF-24, YF-45D, YF-220 and X-273 seem to indicate a deviation from the old "YF-1xx" scheme.

Apart from fake designations, fake USAF serial numbers were reportedly used as well.

Note: Although none of the above is officially acknowledged by the USAF, it isn't denied either, and there is enough evidence available to ascertain that the information given above is essentially correct. For example, the declassification of the Air Force's CONSTANT PEG program in 2006 has allowed former pilots of the USAF's "Red Eagles" and "Red Hats" squadrons (which flew the MiGs) to reveal first-hand information (presented in sources [1] and [2] in list of references below).

Known and Rumoured Numbers

Because the USAF so far doesn't officially acknowledge the use of said cover designations, all numbers presented here are technically rumours only. However, most numbers have been forwarded by reliable sources, and there can be no doubt that they have actually been used for classified programs.

The "References" column indicates the sources of the alleged designations:

[1] Steve Davies: "Red Eagles. America's Secret MiGs", Osprey Publishing, 2008
[2] Peter W. Merlin: "Dreamland: The Secret History of Area 51", Schiffer Publishing, 2023
[3] Aviation Week & Space Technology. In 2000 and 2001, there were a few short notes in AW&ST about the alleged YF-113G aircraft. These notes included some information on the use of YF-1xx designations.
[4] Official USAF biography of Col. Joseph A. Lanni. At the time of this writing, it is not available online, but an archived version can be retrieved from the Internet Archive.
[5] Mr.Z. Z (real name withheld as requested) is a person, who has provided some information as well as the background story how he acquired his data (this story explains why he doesn't know the actual aircraft type associated with each designation). He asked not to reveal his name or background.
[6] Offical USAF biography of Col. Dan Javorsek. The original references to YF-220 and X-273 have since been replaced by "prototype" and "demonstrator aircraft".
[7] Biography of US Navy test pilot Raymond Marshall.

Designations shown in black can be regarded as identified with a high degree of reliability, while those in grey are less certain.

Designation References Remarks
YF-110B [1,2,5] MiG-21F-13 "Fishbed-C/E". The aircraft used in the HAVE DOUGHNUT program used the serial 68-0965. [5] quotes the serials 75-001, 75-004 and 75-010 for other YF-110B's.
YF-110C [1,2] Chengdu J-7B (MiG-21F-13 variant built in China)
YF-110D [1,2] MiG-21MF "Fishbed-J"; used in HAVE COAT program
YF-110E [2] Unknown foreign type used in HAVE PHOENIX program, around 1991
YF-110L [2] Unknown foreign type used in HAVE PHOENIX program, time frame 1986/1992
YF-110M [2] Unknown foreign type used in HAVE PHOENIX program, time frame 1986/1993
YF-112 [1,3] This is mentioned as "used for a MiG". It is likely that this remark only refers to the general use of "YF-112" for ex-Soviet aircraft, and not a specific type. Therefore a plain YF-112 designation (without suffix) probably didn't exist. Suggested candidates for a YF-112 designation include a Sukhoi Su-22 and (less likely) a MiG-19.
YF-112C [2,5] Possibly used as designation for a former East German Su-22M4 "Fitter-K", evaluated in the 1993-1998 time frame
YF-112D [2] Possibly used as designation for a former East German Su-22M4 "Fitter-K", evaluated in the 1993-1998 time frame
YF-113A [2] MiG-17F "Fresco-C" used in HAVE DRILL program
YF-113B [1,2] MiG-23BN "Flogger-F"
YF-113C [2] MiG-17F (actually a Chinese-built J-5) "Fresco-C" used in HAVE PRIVILEGE program
YF-113C [2] Designation re-used for unknown foreign type used in HAVE PHOENIX program, around 1992
YF-113E [1,2] MiG-23MS "Flogger-E"
YF-113G [2,3] Possibly a secret USAF prototype developed and flown in the 1993/96 time frame. There was much speculation about this designation, and it was also said that the YF-113G was a MiG-23 (of unknown subtype). However, the identification of the YF-113G as a U.S. prototype was made by reliable sources quoting a YF-113G pilot's official biography, and must therefore be regarded as confirmed. The MiG-23 story apparently originated from confusion with other YF-113 designations (i.e. YF-113B/E).
YF-113H [2] Unknown foreign type used in HAVE PHOENIX program, around 1987/1988
YF-114C [1,2] MiG-17F "Fresco-C" (incl. the one used in the HAVE FERRY program)
YF-114D [1,2,5] MiG-17PF "Fresco-D". [5] quotes the serial 75-008 as used by a YF-114D.
YF-116A [2] MiG-29 "Fulcrum"; borrowed from Germany in 1991 under HAVE LOAN program
YF-117A (n/a) Lockheed SENIOR TREND stealth fighter. This designation was kept as the official designation when the aircraft was revealed to the public, thus creating the only official post-111 F-designator.
YF-117D [2] Northrop TACIT BLUE
YF-118G [2] Boeing Bird of Prey
YF-24 [2,4] Classified prototype, [2] mentions a first flight in April 1997. The YF-24 designation is the earliest known exception to the YF-1xx scheme, but the number 24 is apparently no coincidence since it follows on from the last known official F-series designator at that time, the YF-23A.
YF-43B [-] Rumoured designation of unclear origin, and unknown time frame of usage.
YF-45D [2,7] Unidentified classified aircraft, time frame 2018/2021
YF-220 [2,6] Classified prototype, time frame 2012/2017
X-273 [2,6] Classified experimental demonstrator, time frame 2012/2017

One known formerly classified aircraft, which is missing from the list, is the Lockheed HAVE BLUE stealth demonstrator. However, this aircraft apparently never received a YF-1xx style designation.





Comments and corrections to: Andreas Parsch



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Last Updated: 26 November 2023