| United States military aircraft serials | |
|---|---|
| 06-6161 a C-17 |
In the United States, all military aircraft display a serial number to identify individual aircraft. Because these numbers are located on the aircraft tail, they are sometimes referred to unofficially as "tail numbers". Individual agencies have each evolved their own system of serial number identification.
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The United States government purchased its first heavier than air aircraft in 1908. The aircraft a Wright Model A was used by the aviation section of the United States Army Signal Corps and was issued with serial number 1. Subsequent aircraft were numbered in sequence.
The aviation section became the United States Army Air Service in 1918 but the sequence of numbers started in 1908 continued without a change. The USAAS became independent from the Signal Corps in 1920 and by 1921 the sequence had reached 68000. On 1 July 1921 a new serial system was introduced based on the United States Fiscal Year which continues to the present day. For example the first aircraft to be procured with fiscal year 1960 funds was a Boeing B-52H which was serialed 60-001.
When the USAAS became the United States Army Air Corps in 1926 the sequence continued unchanged.
When the USAAC became the United States Army Air Force in 1941 the sequence continued unchanged, and the displayed number, normally shown on the fixed vertical stabilizer's sides, usually dropped the first digit of the year of the contract issuance.
When the USAAF became the United States Air Force in 1947 the sequence continued unchanged. Although independent from the Army, Army aircraft continued to be allocated in the same numeric sequence until 1967.
In 1967 the United States Army continued to use the fiscal year serials but the numeric element was started at 15000 for each year. In 1971 the sequence was started at 20000 and was not re-started with each fiscal year.
The United States Navy purchased its first aircraft in 1911, a Curtiss Triad pusher floatplane. The Navy allocated a prefix for each manufacturer and the first aircraft was serialed A-1, with A allocated to Curtiss. Different letters were also allocated to the same manufacturer but for different types of aircraft, for example Curtiss amphibians were allocated E. In early 1914 the system was changed to a two-letter type/sub-type system with each having a sequence starting from 1. A was allocated for heavier-than-air types for example AB was a flying boat and AX was an amphibian. All surviving aircraft from the original system were reserialled.
In 1917 the individual number sequences were stopped and a combined sequential numerical system was started at number 51. Prefix letters were retained for a short time but in 1917 they were replaced with single letter A for aeroplane. The numbers were official designating numbers but became known as Bureau Numbers (BuNos) due their assignment by the Navy Bureau of Aeronautics. The service stopped using the A prefix in 1930 (with the last being A-9204).
When the sequence reached 9999 in 1935 the sequence was re-started at 0001. At the start of the 1940s so many aircraft were purchased that surviving aircraft from the first sequence could be confused with second-series aircraft the sequence was stopped at 7303.
In 1940 the third sequence was started at 00001 (with five digits). When the third sequence reached 99999 it continued with six digits which continues to date.
When the United States Coast Guard purchased their own aircraft in 1926 they were assigned one or two digit serial numbers. In 1934 the system was changed to a three-digit number with the first digit indicating an aircraft type. In 1936 this was changed again and all aircraft (even those withdrawn from use) were allocated serials starting with V101 In 1945 the V prefix was removed and replaced with digit 1 to make a four-digit serial numbers which continue to the present. Since 1969 executive aircraft operated for the Secretary of the Treasury were assigned their own sequence beginning with 1.
The early Army aircraft had large black serials marked on the fin or rudder and in 1917 it was usual to prefix the serial with SC for signal corps or later AS for aerial service. Although later the prefixes were not always marked and were eventually dropped. From 1942 the serial number was applied to the fin (or boom if a helicopter) and the first digit of the fiscal year would be removed but the serial would not be allowed to be less than four digits (for example B-45 serial number 47-007 was marked 7007) but there was no upper limit (for example YP-59A 42-108783 was marked as 2108783).
Because the first digit of the fiscal year was not marked aircraft over ten years old were prefixed with O for obsolete (for example UH-1H 66-16717 later in its career was marked as O-16717), this practice stopped in the 1970s.
In 1956 the fin serials were changed from a minimum of four digits to five digits and in 1957 all serials were limited to five digits (for example KC-135R 58-0001 is marked as 80001) the system is still in use.
In 1969 camouflaged tactical aircraft were marked with modified presentation when the prefix AF was added with the fiscal year underneath followed by the last three digits of the serial number.
Whatever the serial presentation on the fin, the full fiscal serial is always presented in a technical data block which is normally on the port (left) side near the cockpit.
Naval aircraft normally have their serial along with type designation marked in small letters on the rear fuselage. Sometimes the last four digits of the serial are painted on the fuselage or fin. Sometimes the last three digits are used as the side codes but on operational aircraft this is normally a squadron assigned code not a shortened serial number.