During WWII, the RAF used three-letter codes to identify their aircraft from a distance. Two large letters were painted before the roundel, which signified the squadron to which the aircraft belonged, and another letter was painted after the roundel which indicated the individual aircraft. Aditionally, there was the individual serial number for each aircraft, which was painted in a much smaller size, usually somewhere at the rear of the aircraft, either under the tailplane or on the fin. Occasionally the code letters were painted in other places, but their meaning remained the same. These codes were also used by the RCAF, SAAF, RNZAF, USAAF (units of the 8th and 9th AF), and for some time by post-war Belgian units.

As an example, the Hurricane Mk IIb shown above has the letters LK before the roundel, which tells us that it was with No.87 Squadron.

You will also notice that some of the squadrons are highlighted in blue. If you click on these you will be given a short history of each squadron from inception up to the end of hostilities in the Second World War.