1962 United States Tri - Service aircraft designation system The 1962 United States Tri - Service aircraft designation system is a unified designation system introduced by the United States Department of Defense on 18 September 1962 for all the U . S . military aircraft . Prior to this date , each armed service used their own nomenclature system . Under the 1962 system , almost all aircraft receive an unified designation , whether operated by the United States Air Force ( USAF ) , United States Navy ( USN ) , United States Coast Guard ( USCG ) , United States Marine Corps ( USMC ) , or the United States Army . Experimental aircraft operated by manufacturers or the National Aeronautics and Space Administration are also often assigned numbers in the X - series . The 1962 system was based on the one used by the USAF between 1948 and 1962 which was in turn based on the USAAS / USAAC / USAAF system used from 1924 to 1948 . Since it was introduced , the 1962 system has been modified and updated ; in 1997 a revised form of the system was released . Designation system . The designation system produces a " Mission - Design - Series " ( MDS ) designation of the form : Of these components , only the " Basic Mission " , " Design Number " and " Series Letter " are mandatory . In the case of special vehicles a " Vehicle Type " symbol must also be included . Status prefix . These optional prefixes are attached to aircraft not conducting normal operations , such as research , testing and development . The prefixes are : A temporary special test means the aircraft is intended to return to normal service after the tests are completed , while permanent special test aircraft are not . The Planning code is no longer used but was meant to designate aircraft " on the drawing board " . For example , using this system an airframe such as the F - 13 could have initially been designated as ZF - 13 during the design phase , possibly XF - 13 if experimental testing was required before building a prototype , the YF - 13 ; the final production model would simply be designated F - 13 ( with the first production variant being the F - 13A ) . Continuing the example , some F - 13 during their service life may have been used for testing modifications or researching new designs and designated JF - 13 or NF - 13 ; finally after ( many ) years of service , the airframe would be permanently grounded due to safety or economic reasons as GF - 13 . Modified mission . Aircraft which are modified after manufacture or even built for a different mission to the standard airframe of a particular design are assigned a modified mission code . They are : The multi - mission and utility missions could be considered the same thing , however they are applied to multipurpose aircraft conducting certain categories of mission . M - aircraft conduct combat or special operation s while U - aircraft conduct combat support missions , such as transport ( e . g . , UH - 60 ) and electronic warfare ( e . g . , MC - 12 ) . The vast majority of U . S . Coast Guard air assets include the H - code ( e . g . , HH - 60 Jayhawk or HC - 130 Hercules ) . Basic mission . All aircraft are to be assigned a basic mission code . In some cases , the basic mission code is replaced by one of the modified mission codes when it is more suitable ( e . g . , MH - 53 Pave Low III ) . The defined codes are : The rise of the multi - role fighter in the decades since the system was introduced has created some confusion about the difference between attack and fighter aircraft . According to the current designation system , an attack aircraft ( " A " ) is designed primarily for air - to - surface missions ( also known as " attack missions " ) , while a fighter category " F " incorporates not only aircraft designed primarily for air - to - air warfare , but — additionally — multipurpose aircraft designed also for attack missions . The Air Force , supposedly because of unpopularity of battlefield attacks in its ranks , has even assigned the " F " designation to attack - only aircraft , such as the F - 111 Aardvark and F - 117 Nighthawk . At the present time , the only " A " designated aircraft in the Air Force is the A - 10 Thunderbolt II . Of these code series , no normal aircraft have been assigned a " K " or " R " basic mission code in a manner conforming to the system . Vehicle type . The vehicle type element is used to designate the type of aerospace craft . Aircraft not in one of the following categories ( most fixed - wing aircraft ) are not required to carry a type designator . The type categories are : A UAV control segment is not an aircraft , it is the ground control equipment used to command a UAV . Only in recent years has an aircraft been designated as a spaceplane , the proposed MS - 1A . Design number . According to the designation system , aircraft of a particular vehicle type or basic mission ( for manned , fixed - wing , powered aircraft ) were to be numbered consecutively . Numbers were not to be assigned to avoid confusion with other letter sequences or to conform with manufacturers ' model numbers . Recently this rule has been ignored , and aircraft have received a design number equal to the model number ( e . g . , KC - 767A ) or have kept the design number when they are transferred from one series to another ( e . g . , the X - 35 became the F - 35 ) . Series letter . Different versions of the same basic aircraft type are to be delineated using a single letter suffix beginning with " A " and increasing sequentially ( skipping " I " and " O " to avoid confusion with the numbers " 1 " and " 0 " ) . It is not clear how much modification is required to merit a new series letter , e . g . , the F - 16C production run has varied extensively over time . The modification of an aircraft to carry out a new mission does not necessarily require a new suffix ( e . g . , F - 111C s modified for reconnaissance are designated RF - 111C ) , but often a new letter is assigned ( e . g . , the UH - 60As modified for Search and Rescue missions are designated HH - 60G ) . Non - systematic aircraft designations . Since the 1962 system was introduced there have been a number of non - systematic aircraft designations and skipping of design numbers . Non - systematic or aberrant designations . The most common changes are to use a number from another series , or some other choice , rather than the next available number ( 117 , 767 , 71 ) . Another is to change the order of the letters or use new acronym based letters ( e . g . SR ) rather than existing ones . It should be noted that since the DOD has final authority over its own rules , even non - systematic designations are both correct and official . In other words , even though it uses the system as its guideline for naming aircraft , it can approve whatever it chooses , and whatever is approved is " correct " . Skipped design numbers . The design number " 13 " has been skipped in many mission and vehicle series for its association with superstition . Some numbers were skipped when a number was requested and / or assigned to a project but the aircraft was never built . The following design numbers in the 1962 system have been skipped : < nowiki > * < / nowiki > : 24 or 36 depends on future aircraft designations of the DoD . < nowiki > * * < / nowiki > : The X - 23 and X - 39 designations exist , but were never officially assigned . X - 52 was skipped to avoid confusion with the B - 52 Stratofortress . Manufacturers Code . From 1939 a manufacturers code was added to designations to easily identify the manufacturer and the production plant . The code was a two letters for example F - 15E - 50 - MC the MC being the code for the McDonnell Douglas plant at St . Louis , Missouri . Block number . In 1941 block numbers were added to designations to show minor equipment variations between production blocks . The block number appears in the designation between the model suffix and manufacturers code ( for example F - 100D - 85 - NH ) . Initially they incremented in numerical order - 1 , - 2 , - 3 but this was changed to - 1 , - 5 , - 10 , - 15 in increments of five . The gaps in the block numbers could be used for post - delivery modifications , for example a F - 100D - 85 - NH could be modified in the field to F - 100D - 86 - NH . Not all types have used block numbers .