• When introduced in June 1945, tail codes were assigned to individual aircraft carriers. Thus all aircraft based on a particular ship were supposed to carry the ship's code. As of August 1948, tail codes were no longer assigned to aircraft carriers but rather to carrier air groups, which in December 1963 were re-designated as
carrier air wings. • U.S. Navy carrier-based squadrons that deploy as whole units, like fighter and attack squadrons, use their parent carrier air wing tail codes; these types of squadrons are normally not issued individual tail codes. • Other types of the Navy's carrier-based squadrons that normally send detachments to several carriers, like photo reconnaissance, early warning or electronic attack, have frequently received individual tail codes. When deployed, such squadrons usually adopted the tail code of the parent carrier air wing. However, in recent years the practice of assigning individual tail codes to any of the carrier-capable squadrons seems to have been discontinued. • Land-based squadrons of the U.S. Navy – e.g., patrol, transport, observation and other support squadrons – are assigned individual tail codes. The same has been applicable in the past to
Naval Air Stations. • Each U.S. Marine Corps squadron, regardless of its mission, is assigned its own tail code. When a carrier-capable Marine squadron deploys on an aircraft carrier as a part of the U.S. Navy Carrier Air Wing, it typically adopts the tail code of this Air Wing for the period of deployment. • A circular letter issued by the CNO in November 1946 specified that code letters on USMC planes were to be underscored. The underscoring of codes was a short-lived practice abandoned by 1949. • Throughout the history of tail codes there have been a number of duplicates where the same code was used at the same time by more than one unit. This happened frequently during the first post-war decade when the Navy made several revamps of its tail code assignments within a short time frame. Most typically, duplicates resulted when the same letter was assigned to a regular Air Group and to a reserve facility: for example, in the early 1950s the tail code "A" was valid both for Carrier Air Group 15 aircraft and for all Naval Air Reserve units home-based at NAS Anacostia. • In certain cases Navy or Marine aircraft do not carry tail codes. This happened with aircraft wearing special or experimental camouflage paint, particularly during the Vietnam War deployments. Aircraft of Marine Helicopter Squadron One (
HMX-1) employed for VIP transport are another example. • The U.S. Navy and the Marine Corps do not seem to have any specific procedure for removing a tail code from use. If a unit that owned a particular tail code is disestablished, the respective tail code becomes extinct. Later, this code may be assigned to a different unit, or it may remain unused. ==List of navy and marine aircraft tail codes==