Duplications in U.S. Military Aircraft Designation Series

Copyright © 2004 Jos Heyman and Andreas Parsch

Introduction and Scope

This article is a complete listing of all duplications of basic designations in any of the aircraft designation systems used by the U.S. military services since 1919. For an explanation of the current system, see the article about Current Designations Of U.S. Military Aircraft on this site. For details about the earlier designation systems you may refer to this Wikipedia landing page: United States military aircraft designation systems.

In the context of this article, a "duplication" is the use of the same basic designator within one system. This means that the designation "P-3A" in the current system (for the Lockheed Orion patrol aircraft) is not considered a duplication of the USAAC's "P-3A" designation of 1924 (a Curtiss Hawk pursuit plane). On the other hand, in the current system "KC-10A" is considered a duplication of "C-10A", because both have the basic designation C-10.

There are several known (and quite possibly even more unknown) cases where a designation was proposed and/or requested for a certain aircraft, but eventually rejected by the military authorities and thus not officially assigned. Of course, the numbers remained unassigned and were usually proposed again and eventually officially allocated at a later time. Such cases are not considered duplications of a designation. Two examples of designations, which were proposed several times, but in the end never allocated at all(!) are F-109 (USAF 1948/62) and C-16 (DOD 1962-today).

In a few cases the military used a designation for a one-off aircraft, which looked like an official military designation but wasn't. This includes UC-8A for a deHavilland Canada Dash-8 used by the US Navy, and UC-27 for a Fairchild F-27A used by the US Navy. These are not considered duplications of the official C-8 and C-27 designators.

U.S. Army Air Force System, 1924 - 1948


The XP-59 designation was originally used for a twin boom fighter designed by Bell of which two examples were ordered which were subsequently cancelled. It has been suggested the serials 41-19506/19507 were associated with this design.

The designation P-59 was then assigned to the Bell Model 27 Airacomet, the first jet of the USAAF, and three XP-59As were ordered on 3 October 1941. They were fitted with a General Electric Type IA jet and the first flight took place on 2 October 1942. The serials were 42-108784/108786. The YP-59A was a development batch of 13 aircraft with serials 42-108771/108783. Two were transferred to the US Navy with serials 63960/63961 where they either did not receive a designation or received the designation XF2L-1. Also a single aircraft was exchanged with the RAF for a Gloster Meteor. That aircraft became RJ362/G. The P-59A had a longer fuselage and 100 were ordered on 11 March 1944 although only 20, with serials 44-22609/22628 were completed. The cancelled serials were 44-22629/22708 although some serials were used for the P-59B. On 11 June 1948 those remaining in service were redesignated as ZF-59A. The XP-59B was a cancelled version with a single General Electric I63 engine. Development was abandoned in favour of the Lockheed P-80 design. The designation P-59B was assigned to 30 aircraft fitted with J31-GE-5 engines and which received serials 44-22629/22658. Three of these went to the US Navy with serials 64100 and 64108/64109. On 11 June 1948 those remaining in service were redesignated as ZF-59B.

Note: The P-59 designation was re-used for security purposes. If the XP-59A designation were inadvertently leaked, it could have passed as a development of the XP-59 piston-engined fighter.

U.S. Air Force System, 1948 - 1962


The B-26 designation was first used for the Martin Marauder.

On 11 June 1948 the USAF's aircraft designation system was changed to such an extent, that the majority of designation letters was redefined. Among the changes was the removal of the A-for-Attack symbol from the system. Therefore several versions of the Douglas A-26 Invader were redesignated in the B-for-Bomber series. Known redesignations are B-26B, B-26C, RB-26C and XB-26F, whilst, at a later date, more designations were added due to conversions etc. On 11 June 1948 the following Marauder designations were also still in existence: ZB-26B, ZB-26C and ZXB-26H.

Note: This re-use of the B-26 designation is not a "duplication" in the strict context of this article, because the USAF's designation system change of 1948 effectively introduced a new system. It is included here, because it's relatively well-known and its omission would only draw questions ;-).


The designation C-127 was originally assigned to the deHavilland Canada DHC-2 Beaver, but that aircraft was eventually designated L-20 before it entered U.S. military service.

The designation YC-127 was then assigned to a 4-engined Boeing transport project, which was not built.


The YC-137 designation was first used for what became the YC-97J turboprop version of the Boeing C-97 Stratofreighter. Its serials were 52-2693 and 56-2762.

The designation YC-137 was then used for deHavilland Canada DHC-3 Otters, which were ordered with serials 55-2973/2978. They were redesignated as YU-1 before delivery.

Finally the C-137 designator was assigned to the Boeing 707 in U.S. military service. The VC-137A had the model designation 707-153 and three were ordered as Presidential aircraft with serials 58-6970/6972. The first flight was on 7 April 1959. Later the aircraft were converted with Pratt & Whitney TF33-P engines and were redesignated as VC-137B and yet later C-137B. Two commercial 707s were purchased as the next Presidential aircraft as VC-137C with serials 62-6000 and 72-7000 (the latter serial out of sequence). The former flew for the first time on 10 August 1962 whilst the latter flew for the first time on 31 July 1972. They were similar to the VC-137Bs and were eventually redesignated as C-137C. The serials 85-6937/6974 were assigned to two confiscated Boeing 707s which were used as C-137C. The EC-137D was the prototype of the E-3 airborne warning and control (AWACS) aircraft. Two aircraft were procured with serials 71-1407/1408 and the first flight was on 9 February 1972. Two VC-137s were scheduled to be converted in 1998 to a configuration similar to that of the RC-135V.


The XF-106 designation was originally assigned to what became the Republic XF-84H, an experimental turboprop derivative of the F-84H.

The F-106 designation was re-used, when the Convair F-102B was redesignated as F-106A on 17 June 1956. The first flight took place on 26 December 1956 and in total 277 aircraft were built with serials 56-451/467, 57-229/246, 57-2453/2506, 58-759/798 and 59-001/148. Batches with serials 58-799/899 and 59-166/204 were cancelled. One aircraft was modified with two nacelles housing J85 engines to study advanced engine intakes and exhausts. The F-106B was originally designated as TF-102B and TF-106A and was a two-seater model. 63 were built with serials 57-2507/2547, 58-900/904 and 59-149/165 whilst a batch with serials 59-205/240 was cancelled. The first flight was on 9 April 1958. The first eight of these have also been referred to as JF-106B whilst two F-106Bs (57-2507 and 57-2516) were used for permanent tests as NF-106B. On completion of their useful life 65 F-106As and 2 F-106Bs were converted as QF-106A and QF-106B target drones. QF-106A serials were 56-453, 56-454, 56-465, 58-760, 58-764, 58-766, 58-772, 58-774, 58-775, 58-779, 58-780, 58-782, 58-783, 58-786, 58-788, 58-791, 58-792, 58-795, 58-797, 59-002, 59-006, 59-008, 59-010, 59-011, 59-015, 59-020, 59-024, 59-026, 59-027, 59-035, 59-038, 59-046, 59-053, 59-054, 59-056/064, 59-066, 59-072, 59-074, 59-076, 59-077, 59-081, 59-083, 59-085, 59-091, 59-092, 59-096, 59-099, 59-100, 59-110, 59-119, 59-126, 59-130, 59-132, 59-135, 59-136, 59-138, 59-140 and 59-141. The QF-106Bs carried serials 59-152 and 59-159. A proposed development was the F-106C of which 350 were contemplated for production but which were cancelled on 23 September 1958 although two F-106As, 57-239/240, were used as YF-106C in radar tests. The two seat F-106D version was also cancelled, whilst the F-106X designation has been associated to a cancelled remanufacturing programme in competition with the Lockheed F-12.

U.S. Navy System, 1922 - 1962

1) The majority of designation duplications in the old Navy system occured when a manufacturer's code letter was reassigned to a new company after the original one had gone out of business. The numbering sequences for the new manufacturer were always restarted from 1, which led to the re-use of a designation when an aircraft was designed for the same role as one of the earlier manufacturer.
2) Three duplications occurred because in the first year of the system, the sequence of manufacturer and role letter was reversed, and some early designations could be reproduced by coincidence after the letter sequence had been changed. These are not "real" duplications, and are shown in blue in the listing.


The Douglas design was a tandem seat biplane was based on the BuAer design 113. One aircraft was ordered as XFD-1 and with serial 9223. It flew for the first time in January 1933 but failed to meet requirements.

Two McDonnell XFD-1 Phantom jet fighters were ordered on 30 August 1943 with serials 48235/48236. The first flight was made on 21 January 1945. This was followed by an order for 60 FD-1s on 7 March 1945 with serials 111749/111808. The first of these flew on 28 October 1946. Production of a batch with serials 111809/111848 was cancelled. On 21 August 1947 the designations were changed into respectively XFH-1 and FH-1.


The Eberhart Comanche was a single seat fighter. One XFG-1 was ordered by the US Navy with serial A7944 and flew for the first time in June 1927. It was later converted as XF2G-1, with a larger wing and a single float.

The FG designation was later used for the Goodyear licence built Vought F4U Corsair. The FG-1 version was similar to the F4U-1 and 1704 were supplied with serials 12992/14685 and 76139/76148. The first flight was on 25 February 1943. A number of these were converted to FG-1A standard before completion. The FG-1D version was identical to the F4U-1D and 2303 were built with serials 14686/14991, 67055/67099, 76149/76739, 87788/88453 and 92007/92701. A batch with serials 67100/67254 was cancelled. A number of FG-1s were converted with wing mounted radar pods as FG-1E whilst the FG-1K designation was assigned to target drone conversions of the FG-1. With the FG-2 designation not having been assigned, FG-3 was used for 13 FG-1s converted to XF4U-3 standards with an XR-2800-1 engine. The FG-4 designation was applied to a proposed version similar to the F4U-4, with a R-2800-18W engine. Production of 2371 aircraft with serials 67255/67754, 106876/107875 and 115729/116728 was cancelled.


In January 1928 the Eberhart XFG-1 with serial A7944, was fitted with a single float and redesignated as XF2G-1. The aircraft was destroyed in March 1928.

The F2G designation was later used for the Goodyear F2G development for which there was no Chance Vought equivalent. Two FG-1s and five FG-1Ds were converted as XF2G-1 prototypes. The first flight was in May 1944 and known serials include 12992, 13471, 13472, 14691/14695. The aircraft was ordered in production in March 1944 as F2G-1 and F2G-2, the latter being a carrier version. As it was, this order was cut back in May 1945. Only five F2G-1s were completed with serials 88454/88458 whilst 413 with serials 88469/88871 were cancelled. Five F2G-2s were built with serials 88459/88463 with another five with serials 88464/88468 having been cancelled.


The Hall XFH-1 was a single seat fighter with a watertight fuselage and of aluminium construction. A single aircraft was ordered with serial A8009 and flew for the first time in June 1929.

On 21 August 1947 the two McDonnell XFD-1 Phantoms with serials 48235/48236 were redesignated as XFH-1. The XFH-1 had J30-WE-10 engines. On the same day the FD-1, which had flown for the first time on 28 October 1946, was redesignated as FH-1. 60 aircraft were built and the serials were 111749/111808 whilst a batch with serials 111809/111848 was cancelled.


The Berliner Joyce XFJ-1 was a fighter aircraft based on the BuAer design 96. One aircraft was ordered on 16 May 1929 with serial A8288. It flew for the first time in May 1930 and was, after a crash in November 1930 rebuilt as XFJ-2, with a R-1340-92 engine. It flew again on 22 May 1931.

After having been used for the Berliner Joyce FJ in the early thirties, the FJ designation was initially applied by North American to an unswept fighter design and then to a navalised version of the F-86 Sabre. The XFJ-1 was an unswept wing design with a 1 General Electric J35-GE-3 engine. Three aircraft were ordered on 1 January 1945 with serials 39053/39055 and the first flight took place on 27 November 1946. The serials 120339/120341 had also been allocated but not used. The production version was the FJ-1 which was fitted with an Allison J35-A-2 engine. 30 aircraft were ordered on 28 May 1945 with serials 120342/120371 whilst 120372/120441 were cancelled.
The XFJ-2 was essentially a F-86E Sabre with an arrester hook. Similar to the FJ-2, but with a J47-GE-13 engine, two were ordered on 15 January 1951 with serials 133754/133755. The first flight was on 19 February 1952. The FJ-2 was based on the F-86F and 200 were ordered on 30 January 1951 with serials 131927/132126. The first flight was on 22 November 1952. Production of aircraft with serials 129418/129544 and 132127/132226 was cancelled. A single prototype for a close support version, designated XFJ-2B was ordered with serial 133756 on 19 March 1951 and flew for the first time on 27 December 1951.
The XFJ-3 was a FJ-2 modified with a Wright J65-W-2 engine and flew for the first time on 3 July 1953. The serial was 131931. This was followed by 458 production FJ-3s with J65-W-4 engines. The first order was placed on 3 March 1952 and serials were 135774/136162 and 139210/139278 whilst 139324/139423 were cancelled. The FJ-3D designation was assigned to a number of FJ-3s converted as drone directors for the Vought Regulus, whilst the FJ-3D2 was a drone director for the KDA and F9F-6K drones. The FJ-3M was a version of the FJ-3 fitted with two Sidewinder missiles and 80 were built with serials 141364/141443. In addition several FJ-3s were converted to this configuration.
The XFJ-4 was an extensively redesigned aircraft. Two aircraft were ordered with serials 139279/139280 and the first flight was on 28 October 1954. The FJ-4 was the production version fitted with a J65-W-16A engine. 150 were ordered from 4 June 1953 with serials 139281/139323 and 139424/139530. One of these aircraft was used for development testing and was redesignated as YFJ-4. The FJ-4B was a close support version and from 4 June 1953 222 were ordered with serials 139531/139555, 141444/141489, 143493/143643 whilst aircraft with serials 143644/143676 were cancelled. The first flight was on 3 December 1956. A number of these aircraft were used for development testing as YFJ-4B. Following an order placed on 12 August 1955 FJ-4s 139282 and 139284 were converted with an additional Rocketdyne AR-1 engine and were known as FJ-4F.
The FJ-5 was a proposed design in competition with the F11F design. It had an air intake above and behind the cockpit as the F-107 design.
On 18 September 1962 those aircraft remaining in service were redesignated in the as follows: FJ-3 → F-1C, FJ-3D → DF-1C. FJ-3D2 → DF-1D, FJ-3M → MF-1C, YFJ-4 → YF-1E, FJ-4 → F-1E, FJ-4B → AF-1E, YFJ-4B → YAF-1E.


The Loening XFL-1 was a single seat fighter of which one example was ordered with serial 9346 but which was subsequently cancelled.

The Bell 5 Airabonita was a development of the P-39 but with a tail wheel. A single XFL-1 was built with serial 1588 and flew for the first time on 13 May 1940. It failed carrier trials.


The XF2L-1 designation was allocated to two Bell P-63Es transferred from the USAAF with serials 90060 and 90061 but were not taken up. The serials were later used for the two L-39s converted with swept wings. These were converted from a XP-63N and a P-63A and had a 35° swept wing. The first L-39 flew on 23 April 1946.

The designation XF2L-1 was also allegedly used for two Bell YP-59As transferred to the Navy.

The F2L-1K designation was used for two Bell P-39Qs which were transferred to the US Navy as target drones. The serials were 91102/91103. The transfer of aircraft with serials 122447/122451 was cancelled.


The NAF XFN-1 was a projected single seat fighter of which one was ordered with serial A8978 but which was subsequently cancelled.

The SEV-1 was a single seat fighter which flew for the first time in 1937 as a civil aircraft with registration NX-1254. Also referred to as NF-1 and NV-1, it was transferred to the US Navy on 24 September 1937 for evaluation at Anacostia. Some references sources suggest it was designated as XFN-1, however, other sources suggest the NF-1 designation was a company one. This implies that the XFN-1 was, at best, unofficial, or even an "invention" by subsequent historians. Whatever the case, the aircraft was not procured and no serial was assigned. Some reference sources have also suggested that there was a second aircraft with registration NX-1257, although such a registration is not known and may represent a printing error.


The XFO-1 designation was first assigned in 1943 to four Lockheed F-5B Lightnings which were transferred from the USAF to the US Navy in North Africa with serials 01209/01212 . They were later returned. It has also been suggested that they were used in Hawaii as trainers for the F7F.

The XFO-1 designation was later used as the initial designation of the Lockheed XFV-1 Salmon which carried serials 138657/138658 and were redesignated in 1951.

Finally, the FO-1 designation was unofficially assigned to three Lockheed P-80As which were transferred to the US Navy with serials 29667/29668 and 29689 although official sources list these aircraft as P-80A.


Three Fokker T-III torpedo bombers were ordered with designation FT-1 and serials A6008/6010. They were evaluated only.

The Northrop XFT-1 was a single seat shipboard fighter of which a single example was ordered on 8 May 1933 wih serial 9400. It flew for the first time on 16 January 1934 but was damaged in August 1934 following which it received a XR-1510-8 engine. In April 1936 it was fitted with a Pratt & Whitney R-1535-72 engine and was redesignated as XFT-2. It crashed on 21 July 1936.


The FV designation was intended to be used for a version of the F6F Hellcat to be built by Vickers Canada. It is believed that no orders were placed at all.

The designation was again used for the Lockheed 81 Salmon, a tail sitting VTOL fighter to be used with small battleships. Originally designated as XFO-1, two aircraft were ordered as XFV-1 on 19 April 1951 with serials 138657/138658 but only the first one (138657) was completed. The first conventional flight took place on 16 June 1954 with a fixed undercarriage. VTOL was only achieved in flight and no VTOL landings or starts were performed. The aircraft was later fitted with a YT40-A-14 engine. Following the completion of the flight programme, which comprised 32 flights, the aircraft was given to Hiller and ultimately to the San Diego Aerospace Museum. It is believed 138658 is displayed as NAS Los Alamitos. The XFV-2 was the designation of an improved version which was to have an Allison T54-A-3 engine. Neither this aircraft or the production FV-2s were built.


The Atlantic Super Universal was a development of the Fokker transport aircraft designs. A single aircraft was ordered by the US Navy in 1928 for evaluation. It was designated XJA-1 and had serial A8012. It has been suggested the aircraft was cancelled.

The JA designation was later used for the Noorduyn Norseman. The US Navy acquired four USAAF Noorduyn UC-64As as JA-1 and with serials 57992/57994 and 57999. The first three were used in the Arctic regions, the fourth aircraft for general purposes.


Two examples of the Maxson XNR-1 twin engined trainer were procured with serials 1756/1757.

The designation was again used for the Ryan Recruit, a version of the USAAF's PT-21. 100 were built as NR-1 and with serials 4099/4198.


The PB designation was first used for the Boeing model 50 flying boat which was built in 1925 for a transatlantic flight. The US Navy had designated the aircraft PB-1 and given it serial A6881. In 1928 the aircraft was re-engined with 2 Pratt & Whitney GR-1690 and redesignated as XPB-2. It was eventually scrapped in 1932.

The designation PB was the used again for the US Navy version of the B-17 Flying Fortress. On 31 July 1945 the US Navy ordered a single B-17F from the USAAF production line with the designation PB-1 and the serial 34106. The aircraft was brought up to B-17G standards and used for development purposes. In 1946 32 B-17Gs were transferred straight from the production line to the Navy as PB-1W. They received serials 34114, 77137/77138, 77225/77244, 77258, 83992/83998 whilst the transfer of a batch with serials 83999/84027 did not take place. One PB-1W (83992) was used as an engine testbed and was redesignated as XPB-1W. A further sixteen aircraft with serials 77245/77257 and 82855/82857 were converted to SB-17G standards and used by the USCG as PB-1G.


The P2B designation was originally intended for the Boeing 209 design which did not proceed.

The designation was then used for a number of B-29s transferred from the USAAF. The P2B-1S designation was applied to two aircraft used as radar picket aircraft with extra fuel tanks and a radar installation in the bomb bay. The serials were 84028/84029 and they were originally 45-21789 and 45-21787. They were transferred on 14 April 1947. The latter was later used as the launch aircraft for the Douglas Skyrocket and eventually went to NACA as NACA137. A further two aircraft were transferred as P2B-2S with serials 84030/84031.


The XP4Y-1 designation was assigned to the Consolidated 31 Corregidor flying boat which had first flown with civil registration NX21731 on 5 May 1939. It was procured by the US Navy in April 1942 with serial 27852 and flew as such for the first time in July 1942.

In 1952 the P4Y designation was used for the Consolidated Privateer. In 1952 those PB4Y-1Ps remaining in service were redesignated as P4Y-1P whilst those PB4Y-2s remaining in service became P4Y-2. The latter were fitted with R-1840-94 engines. In a similar way PB4Y-2Bs were redesignated as P4Y-2B and PB4Y-2Ss as P4Y-2S. In 1945 nine P4Y-2s were transferred to the USCG as P4Y-2G. They included aircraft with serials 59688, 59882, 66260, 66302, 66304 and 66306. The P4Y-2K designation was used for a number of P4Y-2s converted as radio controlled drones. Those remaining in service on 18 September 1962 were redesignated as QP-4B. Finally the designation P4Y-2P was assigned to a photo reconnaissance conversion of the P4Y-2.


The Fairchild XJQ-2 (a model FC.2) was redesignated as XRQ-2. It had serial A7978.

The RQ designation was again used in 1935 when the USCG acquired a single Stinson Reliant SR5A as RQ-1 with serial 381 (later V149). The aircraft was subsequently redesignated as XR3Q-1.


The Grumman 16 was based on the SF design. The US Navy ordered one XSBF-1 aircraft in March 1935 with serial 9996 and flew for the first time on 24 December 1935. No production was undertaken.

The SBF designation was later used for the Fairchild Canada version of the Curtiss Helldiver. The SBF-1 version was similar to the SB2C-1 and 50 were ordered in 1942 with serials 31636/31685. One of these was used as the XSBF-1 for testing purposes. After the SBF-2 designation had not been assigned, the SBF-3 version was similar to the SB2C-3, fitted with a R-2600-20 engine. 150 were ordered with serials 31686/31835. Whilst the SBF-4 designation was not assigned, the SBF-4E designation applied to aircraft similar to the SB2C-4E and 100 were ordered with serials 31836/31935.


The designation was first assigned to the Curtiss 31 a 3-seat biplane. The model 31 was designed by the Bureau of Aeronautics and 6 CS-1 aircraft were ordered in June 1922 with serials A6500/6505. The first flight took place in November 1922. The production version, known as SC-1 was built by Martin, who underbid Curtiss. 35 were built with serials A6801/6835. The designation CS-2 was applied to a version with a Wright T3 engine and additional fuel capacity. Two aircraft were built as CS-2 with serials A6731/6732 whilst CS-1 A6502 was also brought up to this standard. The production version was designated as SC-2 as well as T2M-1 and 40 were built by Martin with serials A6928/6967. A single CS-2 (A6731) was fitted with a geared engine by Martin in November 1924 as CS-3. It formed the prototype for the production of T3M-1 and T3M-2 aircraft. It is understood the US Navy undertook the CS-4 and CS-5 conversions although no details are available. A single SC-1 was fitted with a Packard 1A-2500 engine and was redesignated as XSC-6. It was A6835. The SC-6 designation was applied to aircraft A6834 also fitted with a Packard 1A-2500 engine whilst the XSC-7 designation was applied to CS-1 aircraft A6503 used as a torpedo bomber.

Later the SC designation was used for the model Curtiss 97 Seahawk, a scout plane which was designed as a floatplane but delivered as a landplane. Two prototypes were ordered on 31 March 1943 as XSC-1 and with serials 34095/34096. The first flight was on 16 February 1944. Later an additional three aircraft with serials 35398/35300 were ordered. The production version was the SC-1 of which 563 were ordered from June 1943 with serials 35301/35797 and 93302/93367. The aircraft were fitted with a fixed landing gear although floatgear was purchased separately. Production of batches with serials 93368/93651 and 111849/111948 was cancelled. A single SC-1 (serial 35302) was fitted with arrester gear and initially designated as XSC-1A and then as XSC-2 and XSC-2A. It had a R-1820-76 engine. The production version was the SC-2 of which 450 were ordered but only ten were completed with serials 119529/119538. The serials of the cancelled aircraft were 119539/119778.


The Detroit TE-1 was a development of the Great Lakes TG design. At that time Great Lakes was subsidiary of Detroit. Whilst the aircraft were ordered as TE-1, they were delivered as TG-2.

The Edo XTE-1 was a tandem two seat version of the OSE design. It is alleged that six OSE-1s were converted but it is doubtful that any were delivered. They were originally ordered with the serials 64575/64576 but were later ordered as 75216/75217. The TE-1 was a production version with serials 75629/75632 and was cancelled. The latter serials have also been associated with the TE-2 version. The aircraft were also designated as XS2E-1.


In 1946 the two Culver XTD4C-1s were redesignated as XUC-1K. Their serials were 120339/120340.

The UC designation has also been used for the De Havilland Canada Otter. The US Navy purchased 16 UC-1 aircraft for use in the polar regions. The serials were 142424/142427, 144259/144261, 144669/144674, 147574, 148322/148323. Those remaining in service on 18 September 1962 were redesignated as U-1B.


The UF-1 designation was assigned to a development of the Vought VE-9 but this aircraft was redesignated UO-1 before completion.

Production of the Grumman G-64 Albatross, the prototypes of which were designated XJR2F-1, was undertaken under the UF designation. There is a substantial amount of transfer of aircraft between the various services and individual aircraft may have had serials applied in the various systems. The UF-1 was the first production version and 104 were ordered with serials 124374/124379, 131889/131918, 137899/137933, 141261/141288, 149822/149824 and 149836/149837. The first flight was on 30 December 1949. The UF-1G was a dedicated Coast Guard version. Six aircraft were ordered by the US Navy for the USCG with serials 142358/142362 which received USCG serials. In addition 28 UF-1s were transferred to the USCG as well as 52 SA-16As from the USAF. The USCG serials include 1240/1243, 1259/1267, 1271/1280, 1288/1294, 1311, and 1313/1317. UF-1L was a winterised version of which two were built outright with serials 142428/142429 whilst others were converted from UF-1s. In addition 5 UF-1s with serials 131914/131918 were converted as UF-1T trainers. The UF-2 version had a larger wing and R-1820-76A engines. 51 UF-1s were rebuilt to this configuration. In addition 19 aircraft were built outright. Also known as UF-2S their serials were 146426/146430, 148240/148245, 148324/148329 and 151264/151265. All except 5 of the UF-1Gs were converted to a standard similar to the UF-2, as UF-2G. In addition 37 USAF SA-16Bs were transferred to the USCG. On 18 September 1962 those aircraft remaining in service were redesignated as follows: UF-1 → HU-16C, UF-1L → LU-16C, UF-1T → TU-16C, UF-2S → HU-16D, UF-2G → HU-16E.


Vought designed a two seat observation aircraft based on the VE.7/9 series. 141 examples were built of the UO-1 with serials A6482/6499, A6546/6551, A6603/6615, A6706/6729, A6858/6877, A6984/7023 and A7031/7050. The UO-1C designation was used for a UO-1 version stressed for use with catapults but the development was never proceeded with. The UO-2 version was fitted with a Wright Hispano E2 and was a UO-1 (A6546) converted as a single seat racer. It was later converted to a two seat utility aircraft. The UO-3 version, of which 20 were ordered, was redesignated as FU-1 before completion. It was fitted with a different wing of a span of 34'2" (10.39 m). The UO-4 designation was assigned to a version of the UO-1 used by the USCG, Two were ordered with serials 4/5, later 404/405 and V104/105. Finally, 15 UO-1s were converted with the UO-3 wing and were redesignated as UO-5. The serials were A6729, A6860, A6866, A6988, A6997, A6999, A7005, A7010, A7011, A7012, A7016, A7035 and A7038.

The US Navy ordered 20 Piper Aztecs as UO-1s with serials 149050/149069 in February 1960. Those remaining in service on 18 September 1962 were redesignated as U-11A.


The UV-1L designation was first assigned to a version of the Lockheed Hercules ordered with serials 148318/148321. Eventually these aircraft were supplied as C-130BL.

The UV-1 designation was then assigned to two Lockheed Jetstars to be used as executive transports with serials 149820/149821. Eventually they were redesignated as C-140C on 18 September 1962 but the aircraft were never delivered.

U.S. Army System, 1956 - 1962


The Sud-Aviation SO1221 Djinn was a light two seat helicopter. The US Army acquired three examples for evaluation with the designation YHO-1 and serials 57-6104/6106. On completion of the trials, in 1958, the aircraft were sold to the French Army.

The HO-1 designation was also briefly used for the Hiller VZ-1 Pawnee. This was a flying platform fitted with a ducted fan. Flight direction was obtained by the pilot leaning into the desired direction. The craft was originally built for the Office of Naval Research to tests ducted fan type of lift and propulsion. Tests began with a twin engined prototype on 21 January 1955 with tethered flights, with a first free flight taking place on 4 February 1955. Tests of the US Army version, with a larger diameter and fitted with three engines and designated VZ-1, began in 1958. Two craft had been ordered in November 1956 with serials 56-6944/6945 and they were initially designated as YHO-1E (in which E designated Hiller).


The designation YHO-2 was initially designated to a military version of the De Lackner DH-4 Aerocycle which was later redesignated as HZ-1. 12 HZ-1s were ordered and presumably built and supplied. The serials were 56-6928/6939. The HZ-1 was a one man flying platform and the first one flew in January 1955.

The designation YHO-2 was then applied to the Hughes light observation helicopter based on the model 269A. Five were ordered as XH-42 with the serials 58-1324/1328 and were later redesignated as YHO-2. The first flight took place in October 1956. Eventually the helicopter was adopted as a primary trainer with the designation TH-55A.

Current Joint Aircraft Designation System, 1962 - today


The deHavilland Canada DHC-4 Caribou was a transport aircraft for 32 troops which flew for the first time on 30 July 1958 as a company aircraft. The US Army ordered five for evaluation as YAC-1 with serials 57-3079/3083 of which the first flew in March 1959. Following this 56 AC-1 production aircraft were ordered with serials 60-3762/3768, 60-5430/5444, 61-2384/2407 and 61-2591/2600. After this production switched to the AC-1A version of which 55 with serials 62-4144/4196 and 62-12583/12584 were ordered prior to the change in designation. On 18 September 1962 those YAC-1s and AC-1s remaining in service with the US Army were redesignated as CV-2A whilst the AC-1As were redesignated as CV-2B. The production of CV-2As with serials 63-7924/7971 was cancelled. The production of the latter version continued as CV-2B with serials 63-9718/9765 and a total of 103 were built. In January 1967 the USAF took over the responsibility of these aircraft and the CV-2A was redesignated as C-7A and the CV-2B as C-7B. Later several aircraft were returned to the US Army National Guard as VC-7A.

The C-7 designation was also used for some versions of the deHavilland Canada Dash-7 in US Army service. The Dash-7 flew for the first time on 27 March 1975 and the US Army aircraft were procured from the civil market in app. 1995. The US Army used one designated as O-5A for imagery intelligence and 2 EO-5Bs as communications intelligence aircraft. The O-5As had civilian registration N5382W, whilst the EO-5Bs had registrations N705GG and N59AG. In addition the US Army used seven aircraft with the designation RC-7 and various RC-7Bs for anti-drug operations and other military intelligence gathering missions. Photographic evidence suggests that the aircraft are operated in a civilian guise and carried the civil registrations including N42RA, N89068, N53993, N176RA, N177RA, N765MG, N54026 and N5382W.

Note: For more information on the RC-7B designation, see RC-7B section in article about Non-Standard DOD Aircraft Designations.


The C-10A designation was first allocated to 11 Handley Page Jetstreams which were ordered by the USAF with serials 68-10378/10392. These were fitted with a strengthened cabin floor and a large cargo door. As Handley Page could not handle the production the programme was cancelled in October 1969 although it seems two aircraft had already flown earlier that year.

In 1978 the KC-10A designation was allocated, out of sequence, to a tanker version of the commercial McDonnell Douglas DC-10 aircraft. The first flight took place on 12 July 1980 and 60 aircraft were procured with serials 79-0433/0434, 79-1710/1713, 79-1946/1951, 82-0190/0193, 83-0075/0082, 84-0185/0192, 85-0027/0034, 86-027/038, 87-0117/0124 and others.


The Lockheed Seastar was a development of the T-33 and was unofficially designated as T-33B. The development was company funded and the first flight took place on 15 December 1953 with the prototype registered N125D. The US Navy placed orders for 150 T2V-1s from May 1954 and with serials 142261/142268, 142397/142399, 142533/142541, 144117/144216 and 144735/144764. Production of batches with serials 144765/144824 and 146058/146237 was cancelled. On 18 September 1962 those aircraft remaining in service were redesignated as T-1A.

In 1990 the designation T-1A was assigned to the Tanker Transport Trainer Aircraft, Beechcraft Jayhawk. The aircraft was based on the Beechjet 400, itself a derivative of the Mitsubishi Diamond 2. There is a requirement for 211 aircraft and production was undertaken by McDonnell Douglas after the dissolution of Beechcraft. Serials are 89-284, 90-398/413, 91-075/102, 92-330/363, 93-621/656, 94-114/148, 94-621/656, 95-004/071. The first flight took place on 5 July 1991. A number of aircraft were used as CT-1B transports.


The T-41A designation was initially assigned to the Grumman TC-4B Gulfstream and an order for the US Navy with serials 151892/151901 was cancelled.

The T-41 designation was then allocated to the Cessna 172 Mescalero, which was a light training aircraft used by civilian contract schools. Aircraft displayed their military serial as well as a civil registration derived from the serial. In total 757 aircraft were built. A number of aircraft were also supplied to foreign forces. 237 examples of the T-41A were ordered by the USAF from 31 July 1964. The serials were 65-5100/5269, 66-8007/8032, 67-14959/14992 and 69-7743/7749. Commencing August 1966, the US Army ordered 255 T-41Bs with a Continental IO-360-D engine for use as trainers and liaison aircraft. The serials were 67-15000/15254. A T-41B with serial 85-24372 was acquired for a foreign customer. The T-41C was similar to the T-41B and 52 were ordered from October 1967 for the USAF Academy with serials 68-7866/7910 and 69-7750/7756. The T-41D was the principal export version and was similar to the T-41B. It was built with serials 68-8944/8977, 69-7181/7200, 69-7274/7279, 69-7675/7692, 70-1592/1607, 70-1962, 70-2021/2027, 70-2037/2061, 70-2456, 71-1051/1062, 71-1458/1467, 71-20940/20943, 72-1334/1336, 72-1384/1385, 72-1408/1437, 72-1470/1475, 73-1579, 73-1659/1663, 74-1724, 74-2093/2096, 74-2113, 75-732/734, 76-1608/1610, 82-668/672.


The T-42A designation was briefly applied to a projected training version of the Beechcraft U-8G Seminole for the US Navy. The designation was changed to TU-8G, but development of the aircraft was cancelled.

The T-42A designation was then allocated to the Beechcraft Cochise, which was an instrument trainer based on the Baron B55. 70 were ordered by the US Army with serials 65-12679/12733, 66-4300/4309 and 71-21053/21057. The latter were supplied to Turkey.


On 28 February 1990, the designation T-48A was officially reserved for the USAF version of the then forthcoming JPATS (Joint Primary Aircraft Training System) aircraft (at the same time, T-49A was reserved for the Navy version). These reservations were not taken up, and JPATS eventually became the Raytheon/Beech T-6A in both services.

The YT-48A designation is also associated with a proposed development of the Cessna T-37 to be in competition with the Fairchild T-46 design. An existing T-37 was to be converted but the conversion did not take place. The T-48 designator probably wasn't officially allocated in that case.

On 13 March 2003, the T-48A designation was finally allocated for the US Navy to a projected replacement for the T-39. The T-48A is planned to be procured under the Undergraduate Military Flight Officer (UMFO) Multi-Place Aircraft Training System (MPATS) program.


Originally the designation U-25A was assigned to the Beechcraft Huron but these aircraft were eventually ordered as C-12A.

The U-25 designation was later assigned to the Dassault Guardian aircraft. The HU-25A Guardian was a special version of the Dassault Falcon for use by the USCG. The aircraft were ordered on 7 January 1977 and the first flight was on 28 November 1977. The serials were 2101/2141. The HU-25B was a version equipped with side-looking radar used for oil spill surveillance and seven HU-25As were converted. The HU-25C designation was applied to nine HU-25As converted to combat drug smuggling.


The Ryan 164 Fleep was a flexible wing research aircraft of which one was built for the US Army and flew for the first time in June 1963. The serial was 63-13003 whilst a second example with serial 63-13004 was cancelled. The designation was XV-8A.

The V-8 designation was also used for the Hawker Siddeley/McDonnell Douglas Harrier V/STOL fighter of the US Marine Corps. The Harrier's AV-8 designation is generally considered as being in the "A"-series (there is no "A-8" as such).
The AV-8A, of which 102 were ordered by the US Marine Corps, flew for the first time on 20 November 1970. The serials were 158384/158395, 158694/158711, 158948/158977, 159230/159259 and 159366/159377. The TAV-8A is a two-seater version of which 8 were ordered by the USMC with serials 159378/159385. The first flight was on 16 July 1975.
Two AV-8As (158394/158395) were converted by McDonnell Douglas as YAV-8Bs and the first flew as such on 9 November 1978. The production version, the AV-8B flew for the first time on 5 November 1981 against an order placed on 12 April 1979. The serials include 161396/161399, 161573/161584, 162068/162090, 162721/162747, 162942/162973, 162964/162970, 162972, 162973, 163010/163021, 163176/163179, 163181/163185, 163187/163190, 163192/163195, 163197/163201, 163203/163206, 163419/163426, 163514/163519, 163659/163690, 163852/163855, 163862/163870, 163873/163883, 164113/164119, 164123/164154, 164540/164571, 165001/165035, 165305/165312, 165354/165357, 165380/165391, 165397/165399, 165417/165432, 165451/165454, 165566/165597, 165652/165659, which included aircraft rebuilt as AV-8B+ and which were given new serials. Batches with serials 162748/162752, 163348/163394 were cancelled. The TAV-8B was a training version which flew for the first time on 21 October 1986. Serials included 162747, 162963, 162971, 163180, 163186, 163191, 163196, 163202, 163207, 163856/163861, 164120/164122, 165036. The designations NAV-8B and NTAV-8B were used for test aircraft.
The designation YAV-8C has been assigned to two AV-8As fitted with improved electronics and which were the prototypes for the conversion of another 47 AV-8As as AV-8C. Serials included 158700, 158706, 158949, 158957, 158958, 158962, 158964, 158972, 158973, 158977, 159232, 159243, 159247, 159254, 159258 and 159370. Similar conversions of AV-8Bs were designated as AV-8D.
The designations AV-8S and TAV-8S were assigned to 11 AV-8As (159557/159562 and 161174/161178) and two TAV-8As (159563/159564) supplied to Spain. They are sometimes also referred to as EAV-8A. They are different from earlier AV-8A and TAV-8A which were also supplied to Spain. Whilst the latter are resp. Mk50 and Mk54, the former are respectively Mk55 and Mk58. Spain also received the EAV-8B version with serials 163010/163021.

Note: For more information on the re-use of the V-8 designation, see AV-8 section in article about Non-Standard DOD Aircraft Designations.


Initially the V-12 designation was assigned to a version of the Pilatus Porter. Known as OV-12A 25 aircraft were ordered in 1968 with serials 157102/157126 from Fairchild Hiller. The aircraft were to be used for river patrol duties in South East Asia. Because of political difficulties the order was cancelled although the project was more or less revived as the AU-23A.

The V-12 designation was then re-used, when the Rockwell NR-356 was designated as XFV-12A. The XFV-12A was a VTOL aircraft to be used for Sea Control Ships. It used thrust augmented wing concept and two aircraft were ordered in 1972 with serials 161080 and 161081. The first flight was expected to take place in October 1974 but the programme was delayed and restricted to one aircraft only which rolled out on 26 August 1977. The aircraft went through a series of captive tests in which it failed to lift its own weight and the programme was eventually cancelled before a flight took place.

Note: No reasons for the re-use of the V-12 designation are documented. However, the next number in line would have been V-14 (assuming that -13 would have been skipped as usual), and maybe the Navy wanted to avoid having both F-14 and FV-14 types under development (or eventually in service). If this is true, then the V-14 designator was avoided twice for very similar reasons. The NASA didn't accept the XV-14 designation for their Bell Model 301 Tiltrotor aircraft either (it became the XV-15), because of fear of confusion with the contemporary Bell X-14 VTOL testbed.

Comments and corrections to: Andreas Parsch

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Last Updated: 23 July 2004