Current Designations of U.S. Military Aircraft
Copyright © 2003-2006 Andreas Parsch
2 The Designation System
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  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(I) (formerly Air Force Joint Instruction 16-401) Designating and Naming Military Aerospace Vehicles (PDF file, 480 kB), dated 14 March 2005. AFI 16-401(I) 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(I). 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.
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):
*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:
(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:
(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:
(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), 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). For more information on these and other examples, see article on Non-Standard DOD Aircraft Designations. Also, sometimes numbers are skipped in one series because they are 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. a currently produced F-16C is much different from an early production F-16C.
(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:
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:
(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(I), 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:
 AFR 66-11, AR 700-26, BUWEPSINST 13100.7: "Designating, Redesignating, and Naming of Military Aircraft", 1962 and 1968 editions
 Department of Defense: "Model Designation of Military Aircraft, Rockets and Missiles", 7/1964, 1/1965, 7/1965, 1/1970 editions
 Department of Defense Publication 4120.15-L: "Model Designation of Military Aerospace Vehicles", 1974, 1977, 1986, 1987, 1990, 1993, 1996, 1998 and 2004 editions
 AFI 16-401(I), AR 70-50, NAVAIRINST 13100.16: "Designating and Naming Military Aerospace Vehicles"
 Department of Defense Aircraft Nomenclature Records
Comments and corrections to: Andreas Parsch
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