The Commonwealth Gazette of 31 March 1921 announced the formation of the Australian Air Force. On this day the AAC was disbanded and replaced by the Australian Air Force (AAF) as a separate service. The prefix Royal was granted soon after and promulgated on 31 August 1921.
A series of prefixes were designed to identify specific areas or materials within the air force, some of which are still widely in use to this day. Prior to this system of identification aircraft had been using RFC/RAF serial numbers.
It is often mistaken that the A in the aircraft's serial number stands for Australia when it is merely just the group identification code. With the introduction of the N prefix for the Navy's aircraft it is also possible to assume the A stands for Air Force or Army depending on the aircraft itself.
With the assigning of the A prefix for aircraft it was also decided that aircraft should be assigned its own identifying number for each type than another number for each individual aircraft.
Often aircraft either built locally or those impressed from civilian sources, as well as several overseas types, were assigned numbers in sequential order starting at 1 however, gaps in the numbering sometimes occurred for unknown reasons. However, not all serial numbers are applied like this with a number of notable exceptions as there is no set standard in assigning individual aircraft numbers.
To date there has been three separate groups or Series as they are known as, each covering different periods and what initially began as a RAAF system has now become standard for the ADF.
First Series (1921 - 1934)
This First Series consisted of only 13 aircraft but only 12 ‘A’ numbers were assigned. This was a result of the order for the 'A5' Vickers Vimy not being taken up and the re-assigning of the A5 prefix to the Westland Wapiti. All aircraft were numbered sequentially.
Second Series (1935 - 1960)
Most of the aircraft in this series were operated by the RAAF during World War II, which made the RAAF one of the top five largest air forces, behind the air forces of Britain, Russia, U.S.A and most likely Canada depending on which figures are used. Many of the aircraft served in small numbers, operating in the Communications, Liaison or Air Ambulance roles while others served in great numbers of 500 or more. With such large numbers of aircraft in use numerous gaps in the serial numbers appeared.
Many aircraft types were received from Britain during this period yet several types including the Fairey Battles, Avro Ansons and the Boeing (B-29) Washington, operated under their RAF serial numbers. For reasons unknown RAAF ‘A’ numbers had been assigned to these aircraft but not applied. Of particular interest is the fact that only the first 48 Avro Ansons had RAAF serials applied yet almost 1000 others retained their previous RAF identity.
Of the 100 aircraft in this series only several serial numbers were held in reserve for aircraft that were either ordered or tested by the RAAF but never accepted into service.
Third Series (1961 - Present)
Most of the aircraft in this series had their serial numbers generally based on their manufacturer’s construction numbers and only a few were numbered sequentially. The McDonnell Douglas F-4E Phantom II, leased from the USAF, retained and flew with their USAF identities but were assigned the spurious 'A69' prefix for administrative purposes only. The number 69 was used as it was derived from the Fiscal year of funding for the aircraft's construction.
When Army Aviation finally obtained its own aircraft independent of the RAAF, serial numbers were assigned in line with the RAAF 'A' number sequence. In 1989 the Army finally wrested control of the rotary winged aircraft fleet from the RAAF although this change did not affect serial numbers.