Current Designations of U.S. Military Aircraft

Copyright © 2003-2023 Andreas Parsch

1 Introduction

2 The Designation System

3 Sources

1 Introduction

The current designation system for U.S. military aircraft was introduced by the Department of Defense in 1962. It was based on the system used by the U.S. Air Force between 1948 and 1962, and replaced the older systems used by the U.S Navy (and Marine Corps) and the U.S. Army. Existing aircraft which used designations not compliant with the new system (all Navy and Marine Corps, many Army, and a few Air Force aircraft) were redesignated effectively on 18 September 1962 (see source [1] and article on Aircraft Redesignations in 1962). The designation system has since been slightly revised and extended, and the latest version is defined by Air Force Instruction (AFI) 16-401 (formerly Air Force Joint Instruction 16-401) Designating and Naming Military Aerospace Vehicles, dated 3 November 2020. AFI 16-401 not only covers aircraft designations, but also the designations of unmanned vehicles (missiles etc.) and some of the bureaucratic red tape to be followed for actually assigning a name or a designation to a military aerospace vehicle.

According to the rules, all aircraft operated by the U.S. military services (Air Force, Navy, Marines, Army) are to receive an official designation as defined in AFI 16-401. In practice, however, all services operate a few off-the-shelf aircraft under the manufacturers' designations. The U.S. Coast Guard also allocates military designations to most of its aircraft, and the NASA uses the X-for-Experimental designation series extensively for its own research aircraft.

The purpose of this article is to present an overview of the aircraft designation system together with notes explaining the details and some exceptions. The missile designation system is covered in the article on Current Designations of U.S. Unmanned Military Aerospace Vehicles, and the actual process of allocating a designation is explained on the page about Allocation of Official Aerospace Vehicle MDS Designations.

2 The Designation System

A U.S. military aerospace vehicle designation is also known as an "MDS Designation". MDS stands for "Mission-Design-Series", naming the three most important components of the designation. An MDS looks as follows (all examples are real-world designations):

Examples:    F - 15 E    Eagle
E A - 6 B Prowler
N K C - 135 A Stratotanker
Y R A H - 66 A Comanche
M Q - 9 A Reaper
C H - 47 F Chinook
Y F - 23 A
X V - 6 A Kestrel
Y V - 22 A Osprey *
EK A - 3 B Skywarrior *
(6) (3) (2) (1) (4) (5)

*Note: The last two MDS designations are not strictly conforming to the regulations, as will be shown below.

In the following section, each of the six elements is explained in detail. For all letter symbols a year range is given in brackets to document when this particular symbol is/was valid. If one of the bounds is given as a range (e.g. 1978/86), this means that I don't know the respective year more exactly.

(1) Vehicle Type: All aircraft which are not "normal" aeroplanes (i.e. powered, fixed-wing, heavier-than-air, non-VTOL, manned, atmospheric aircraft), use one of the following symbols to designate the type of aerospace craft:

Notes for Vehicle Type Symbol:

  1. "D" applies to integrated ground control equipment for unmanned aerial vehicles. I.e., items designated in the "D" series are not aerospace vehicles!
  2. "G" includes motorgliders, which can be routinely used for unpowered flight.
  3. The "Q" series has been introduced to designate reusable unmanned aerial vehicles. The xQM missile designations (see Current Designations of U.S. Unmanned Military Aerospace Vehicles) are now only used for target drones.
  4. "S" is to designate manned aerospace planes, which can operate both within and outside the atmosphere. However, the "S" type symbol is ill-chosen, because it conflicts with the S-for-Antisubmarine mission symbol (see section (2) below). An MDS like "ES-3A", which in fact designated an electronic warfare derivative of the S-3A antisubmarine aircraft, could equally be read as the designation for an electronic warfare spaceplane. So far, this was not an issue, because the only spaceplane designation assigned so far is "MS-1A" (a cancelled project), while the S-for-Antisub series only has the S-2 and S-3 members.
  5. The "STOL" part of the "V" definition is not very well defined, and the decision whether some aircraft with a shorter-than-usual takeoff run is designated as a STOL or a "conventional" aircraft is essentially arbitrary.
  6. "Z" was included in the original revision of the system in 1962 to cover the redesignation of some obsolete Navy airships of the time. When these were gone for good, the "Z" symbol was dropped, only to be reintroduced later when the Navy had new plans for LTA craft.

(2) Basic Mission: The letter to the left of the dash (or the vehicle type symbol) designates the basic mission of the aircraft. Because both basic mission letter in "normal" and vehicle type letter in "special" aircraft are immediately to the left of the dash (and define in which series the MDS is numbered, see section (4) below), both groups of letters have to be distinct to avoid ambiguities, but this rule was violated with the introduction of the S-for-Spaceplane vehicle type symbol. Designations, which include a vehicle type symbol, must also include at least one basic or modified mission (see section (3) below) symbol to designate the mission of the "special" aircraft (i.e., the designation YV-22A is not conforming to the regulation). The following basic mission symbols are defined:

Notes for Basic Mission Symbol:

  1. "F" not only covers air-to-air fighters, but also explicitly includes ground-attack aircraft with only a secondary air-to-air capability. I.e., a combat aircraft with limited air-to-air capability is to be designated as F-for-Fighter even if it is primarily designed for air-to-ground missions. Therefore the change of F-22A to F/A-22A (which has by now been reverted) not only created an invalid designation (slashes are not allowed), but was also completely superfluous.
  2. No designations were ever assigned in the K-series (all tankers were derivatives of other aircraft), which is presumably the reason why the "K" basic mission symbol was dropped.
  3. The "L" basic mission symbol is inconsistent with the rest of the system, because it designates a type of equipment instead of a mission or role. It was only introduced to get a "special" designation for the YAL-1A "Airborne Laser" aircraft (see also article on Non-Standard DOD Aircraft Designations).
  4. No regular designations were assigned so far in the R-series. For a discussion of the non-conforming TR-1A and SR-71A designators, see article on Non-Standard DOD Aircraft Designations.
  5. Many of the more recent designations in the X-series were allocated to unmanned aircraft, which was not the originally intended purpose of the designation system.

(3) Modified Mission: To the left of the basic mission symbol an optional modified mission letter can be used, when an aircraft is used for a different purpose than originally designed. The regulations say that not more than one modified mission letter can be used, but this rule has been violated a few times, e.g. in the EKA-3B designation. Designations, which include a vehicle type symbol, can optionally omit the basic mission letter if a modified mission letter is used instead (as shown by the MQ-9A example). The modified mission symbols are in general the same as the basic mission symbols, but add a few more letters. The following modified mission symbols are defined:

Notes for Modified Mission Symbol:

  1. The original "M" (Missile Carrier) modified mission symbol was needed for the redesignations in 1962, because the U.S. Navy had a special designation letter for missile-capable variants of otherwise missile-less aircraft. However, it was never used after 1962 (when missile armament was a common feature anyway) for new designations, and was therefore eventually dropped. It was briefly replaced by "Mine Countermeasures" before the final "Multimission" meaning was assigned.
  2. The "V" symbol was originally used for all staff transport aircraft, but is nowadays limited to aircraft used by the President of the United States.

(4) Design Number: Each vehicle type and basic mission symbol is used to form a separate series of design numbers. E.g., all helicopters are designated in a single numerical sequence, while "normal" aircraft are designated in separate series according to their basic mission. According to the instructions, the numbers in each series are to be assigned in strict numerical sequence without reference to manufacturers' model numbers and/or existing numbers in other MDS series. However, this rule is rather often violated nowadays, e.g. by using the manufacturer's model number (e.g. KC-767A, MH-139A), retaining the number when a new designation in another series is assigned (e.g. the production variant of the X-35 was designated F-35, although the next number in the F-series was 24), or allocating "special" numbers (e.g. X-50A, T-6A, B-21A). For more information on some of these and other examples, see article on Non-Standard DOD Aircraft Designations. Also, several times numbers were skipped in one series because they were in use at the same time in another series (e.g. C-34 was skipped to "avoid confusion" with T-34).

(5) Series Letter: Variants of a basic aircraft type are designated by a suffix letter. The first model always receives suffix "A" and subsequent series letters are to be assigned in strict sequence (omitting "I" and "O" to avoid confusion with numerals "1" and "0"). The series letter is actually a mandatory component of a conforming MDS, and therefore "plain" designations like "F-16" always designate the general type of aircraft and never a specific model. Of course, the sequence rule is often ignored and there are many designations with out-of-sequence suffixes (e.g. to designate a specific customer, like the "N" in F-16N designated "Navy") or even "special" suffixes as in AV-8B(R)+. It is not well defined, which kind of modifications actually mandate the assignment of a new series letter. In the more recent past, even extensive modifications to an aircraft type have sometimes not led to a different series designation, e.g. the latest version of the F-16C is much different from an early production F-16C.

Theoretically, the regulation even covers the situation that new series letters are needed after "Z" has been reached. In this case, the next available design number is to be used and the series restarted at "A". In practice, this has never happened so far, and is actually quite unlikely to ever happen. More likely, a unique MDS will be established by reusing previous series letters with different modified mission symbols (e.g. AH-1E for a modified AH-1S, not conflicting with the much older UH-1E dsignation).

(6) Status Prefix: Any aircraft, which is not in normal operational service, can receive a prefix letter in its designation to reflect its current status. Because both modified mission and status prefix letters can appear to the left of the basic mission symbol, both groups of letters are distinct to avoid ambiguities. The following status prefixes are defined:

Notes for Status Prefix Symbol:

  1. The "e" prefix is only applied in the initial development phase of an aircraft.
  2. A "J" prefix is used if the aircraft is planned to be converted back to standard configuration after the tests have ended. The "N" prefix is used for aircraft, which are modified so extensively for special tests, that a reconversion to the original configuration is neither planned nor feasible at reasonable costs.
  3. Although the "Z" status prefix is still listed in the regulations, it is nowadays rarely used. Current aerospace vehicle projects very rarely receive a designation before the actual prototype is under construction, and even if they do the "Z" prefix is often not applied.

There are three additional elements of a military aircraft designation, which are not part of the MDS proper, but which are nevertheless often encountered. These elements can be seen in the designations:

Examples: F-15E - 51 - MC    Eagle
EA-6B - 40 - GR    Prowler
(MDS) (8) (9)    (7)

(7) Popular Name: Many U.S. military aircraft have an official "popular name" assigned. This official name can't be assigned by the manufacturer and/or DOD customer at will, but has to run through an approval process in which proposed names are checked for conflicts with existing names (both military and commercial) and their "political correctness". Of course, official names tend to be disregarded by the people actually flying or maintaining the aircraft.

(8) Block Number: Block numbers are not part of the official MDS designation, and their use is optional to the various DOD services. In fact, block numbers are used for some production aircraft (e.g. the F-15) but not all. Block numbers were introduced by the U.S. Army Air Force in World War II to distinguish between minor sub-variants of a specific aircraft variant, and were originally assigned in steps of five (1, 5, 10, 15, ...), with the gaps being intended to be used for modifications after production. This was also the rule for block numbers as defined in the first issue of the current designation system in 1962. The current AFI 16-401, however, defines block numbers as optional and doesn't state any rules for their actual application. In fact, there are several aircraft types where the block numbers were assigned in strict sequence from 1 up, leaving no gaps. It also seems that the USAF doesn't generally use the "dash-number" nomenclature any more, e.g. the latest B-2A update is generally referred to as "B-2A Block 30" and not "B-2A-30".

(9) Manufacturer Code Letters: The original designation system as defined in 1962 also mandated the use of a two-letter code suffix to identify the manufacturing plant of an aircraft. Like the block numbers, these code letters were introduced by the USAAF during World War II. However, manufacturers' codes were officially dropped from the regulations in 1976. Therefore they are definitely no longer mandatory, and even their optional use has apparently essentially ceased. The list of code letters as defined in 1962 follows:

3 Sources

[1] AFR 66-11, AR 700-26, BUWEPSINST 13100.7: "Designating, Redesignating, and Naming of Military Aircraft", 1962 and 1968 editions
[2] Department of Defense: "Model Designation of Military Aircraft, Rockets and Missiles", 7/1964, 1/1965, 7/1965, 1/1970 editions
[3] Department of Defense Publication 4120.15-L: "Model Designation of Military Aerospace Vehicles", 1974, 1977, 1986, 1987, 1990, 1993, 1996, 1998 and 2004 editions
[4] AFI 16-401, AR 70-50, NAVAIRINST 13100.16: "Designating and Naming Military Aerospace Vehicles"
[5] Department of Defense Aircraft Nomenclature Records

Comments and corrections to: Andreas Parsch

Back to Home page

Last Updated: 28 November 2023