Tail codes are markings usually on the vertical stabilizer of U.S. military aircraft that help identify the aircraft's unit and/or base assignment. This is not the same as the serial number, bureau number, or aircraft registration which provide unique aircraft identification.
Since 1993, the U.S. Air Force (USAF), Air Force Reserve, and Air National Guard (ANG), except Air Mobility Command (AMC) aircraft, utilize this format in all tail codes: two large letters, followed by two digits printed in a smaller text size, followed by three more digits printed in a larger text size.
The first two letters identify the home base, or in some organizations, a historic legacy, such as "FF" ("First Fighter") for the 1st Fighter Wing[a] or "WP" ("Wolf Pack") for the 8th Fighter Wing. ANG units usually use the two-letter state/territorial USPS mailing abbreviation as a tail code, though there are exceptions, such as the 110th Airlift Wing using "BC" ("Battle Creek") instead of the "MI" used for other Michigan Air National Guard units. The small digits indicate the fiscal year (FY) the aircraft was ordered. The large digits are the last three digits of the aircraft's serial number.[1][2]
All aircraft assigned to a unit, or in the case of ANG units, the entire state, use a common code. Typically, units of different commands co-located at the same base use different codes. For example, the 509th Bomb Wing at Whiteman AFB uses "WM" while the 442nd Fighter Wing of the Air Force Reserve at the same base uses "KC."
AMC aircraft do not use two-letter identification codes.[3] They have the name of the base written inside the tail flash and a five-digit number in which all digits are printed in the same size. In most cases, the first digit represents the last digit of the fiscal year, and the remaining digits identify the four-digit sequence number. In cases where more than 10,000 aircraft were ordered in a single year (1964, for example), the complete 5-digit sequence number - without FY identification - is used.
The U.S. Marine Corps and U. S. Navy share the same system. USMC squadrons use two letter codes unique to each squadron. The codes are squadron specific and do not identify either the Marine Air Group (MAG) nor the Marine Air Wing (MAW) to which the squadron belongs nor the air station at which it is based. The exception is those squadrons assigned to a Navy Carrier Air Wing which use the Carrier Air Wing's tail code.
Light transport aircraft assigned to Marine Corps Air Stations use a two place tail code consisting of a number 5 followed by a letter unique to each Marine Corps Air Station.