Some squadrons have an individual tradition of presenting their squadron number in Roman numerals or using a suffix to their squadron number (such as "(F)" for "Fighter", "(B)" for "Bomber" or "(AC)" for "Army Co-operation") to indicate a past or present role. An example would be No. 18 (Bomber) Squadron RAF which currently actually operates the heavy-lift Chinook helicopter. However, these practices have, at least in the past, been deprecated at higher levels and generally only apply to certain squadrons with long traditions, especially those numbered from 1-20. Historical Squadrons can choose to 'lay up' their standards at RAF Cranwell or in places of worship following disbandment.
Flying training units and operational evaluation squadrons have generally been (Reserve) squadrons, although they are regular active-duty units. The policy of the (Reserve) numberplate was rescinded in February 2018, to coincide with the renaming of 22 (Training) Group to just 22 Group in line with other RAF Groups.
Some Squadron names include the location they were originally formed.
During the First World War, in order to avoid confusion with similarly-numbered British flying squadrons, units of the separate Australian Flying Corps were known for administrative purposes as 67, 68, 69, and 71 squadrons. Since the Second World War these numbers have always been used by RAF units.
However, the designation 70 (or LXX) Squadron has always been used for RFC/RAF units.
The first squadrons to carry numbers above 200 were former RNAS squadrons that were renumbered upon amalgamation with 200 added to their RNAS squadron number. Independent flights of the RNAS were grouped together in squadrons and given numbers in the 200 series.
Squadrons in the 300–352 series were staffed during the Second World War by volunteers from countries in occupied Europe. In some cases, these RAF squadrons and personnel were regarded by a relevant government-in-exile as serving concurrently with its air force.
(Note: the RAF has never had a flying unit named 314 Squadron, although it has used the number for No. 314 Technical Services Unit. A proposed 314 Squadron was allocated squadron code "UY" during the period April to September 1939, but was never formed.)
Note: the RAF never had a No. 319 Squadron; the "Polish Fighting Team" was attached to No. 145 Fighter Squadron. A proposed 319 Squadron was allocated squadron codes VE for the period April to September 1939. There was also 663 Artillery Observation Squadron; No. 138 Special Duty Squadron Polish Flight "C" and No. 1586 Polish Special Duty Flight.
Note: Nos. 323 to 325 Squadrons were not formed, but allocated Squadron Codes GN, PQ and EA respectively for the period April to September 1939. However these numbers were used for post-war Royal Netherlands Air Force squadrons.
Article XV squadrons of World War II (Nos. 400–490)
Under Article XV of the British Commonwealth Air Training Plan, the air forces of Australia, Canada and New Zealand formed squadrons for service under RAF operational control. Most were new formations, however some had already existed prior to the creation of Article XV and had already been operational during the war, including combat operations.
Note: No No. 599 Squadron seems to have been formed. There were to have been Reserve squadrons using numbers 551–566 which would have been created by adding 500 to existing Operational Training Unit designations. In the event the plan was never put into effect, although there was some desultory use of some of the numbers by some of the OTUs for a short period. Despite their lack of formal activation, this block of numbers has never been re-allocated for use by other units.
Advanced Training Squadrons (550–565)
In the event of a German Invasion the Operational Training Units would have been re-formed into the Squadrons below, under plans as part of Operation Saracen, formulated in Spring 1940, which were later revised as Operation Banquet. Some reserve Squadron numbers were used by their respective OTU's during operational tasks until at least May 1944.
Note: No. 606 Squadron RAF was allocated Squadron codes BG for the period April to September 1939, but was not formed. A non-flying No. 606 Helicopter Support Squadron of the RAuxAF was later formed in 1999.
Note: Nos. 629, 632–634, 636–638, 641–643 and 645–649 were never formed, but some were allocated Squadron codes for the period April to September 1939 – 629 (LQ), 632 (LO), 636 (VZ), 637 (UK), 638 (PZ), 641 (EV), 645 (KF), 646 (YG), 647 (ZS), 648 (YT) and 649 (HA). However a fictitious "633 Squadron" was featured in the eponymous novel and film. In addition, a fictitious 641 Squadron featured in the film "Mosquito Squadron". Also, RAF Volunteer Gliding Squadrons (formerly Volunteer Gliding Schools until 2005) have been numbered in the range 611 to 671 since 1955.
Air Observation Post squadrons
These squadrons were formed during the Second World War to perform artillery spotting and liaison roles, in co-operation with Army units. Most AOP squadron aircrew were provided by the Army. Nos. 661–664 and 666 Squadron were re-formed as Royal Auxiliary Air Force units in 1949. Nos. 651, 652 and 656 Squadron were transferred to the Army Air Corps in 1957.
Note: Nos. 693–694 and 696–699 Squadrons were never formed.
Fleet Air Arm squadrons
While still under the control of the Royal Air Force, flights of the Fleet Air Arm (FAA) were organised into squadrons with numbers in the 700 and 800 range. The range 700 to 750 had been previously used for Fleet Air Arm Catapult Flight numbers.
These squadrons were transferred to the Royal Navy (RN) in 1939, becoming Royal Naval Air Squadrons (RNAS). The 700 and 800 range of squadron numbers continued to be used by the Royal Navy for newly formed Royal Naval Air Squadrons.
Training Depot Stations
Training Depot Stations (TDS) were still in use after the formation of the Royal Air Force in 1918.
Initially formed as Volunteer Gliding Schools, these squadrons retained their gliding school numbers when reformed as squadrons. Conflicts with the main Squadron numbers resolved by the VGS suffix. These Squadrons operate the Viking TX.1 glider.
RAF College Cranwell stores some Standards for disbanded Squadrons that have the potential to be re-activated in the future, preserving the heritage of historic units. Once a Squadron Standard is 'laid up' in a place of worship, upon the disbandment of the Squadron, that Standard can no longer be reactivated. Many UK churches have Standards from the RAF following a service of Disbandment. However, some Squadrons choose to lay up their Standards in College Hall at RAF Cranwell, the spiritual home of the RAF, and may be reactivated as active Squadrons in the future. Old disbanded squadrons that have laid up their Standards can be presented new Standards to reactivate them, but this is currently extremely rare.
Squadron Standards (and their last operated aircraft) that are on display in the College Hall Rotunda in order of seniority are:
Most units of the Royal Air Force are identified by alphabetical (or similar) characters, known as a "squadron code", that is painted on all aircraft belonging to that unit. When individual units are assigned unusually large numbers of aircraft, multiple squadron codes have been used.
Other air forces, especially those from other Commonwealth countries, have often used similar systems of identification. During the Second World War, when units from other air forces were attached to the RAF – such as the Article XV squadrons (also known as "400 series squadrons") – their squadron codes were often changed, to avoid confusion with RAF units.
Historically, the codes have usually been two letters of the alphabet, painted on the rear fuselage next to the RAF roundel. These formed a suffix or prefix to the call sign of each aircraft (on the other side of the roundel) which was usually a single letter (e. g. "G for George"). In general, when an aircraft is lost or withdrawn from use, its call sign has been applied to its replacement or another aircraft.
^RAF Squadrons 901 – 980, Air of Authority Archived 11 January 2011 at the Wayback Machine
Halley, James J. The Squadrons of the Royal Air Force & Commonwealth 1918–1988. Tonbridge, Kent, UK: Air Britain (Historians) Ltd., 1988. ISBN 0-85130-164-9.
Jefford, C.G. RAF Squadrons, a Comprehensive record of the Movement and Equipment of all RAF Squadrons and their Antecedents since 1912. Shropshire, UK: Airlife Publishing, 1988 (second edition 2001). ISBN 1-85310-053-6.
Lake, Alan. "Flying Units of the RAF".Airlife Publishing. Shrewsbury. 1999. ISBN 1-84037-086-6