[Graham Boak]

It's often a good guide but cannot be relied upon. There's a thread running on Britmodeller that says this did apply to 92 Sq Spitfires in early 1940, and I notice that it applied to the early delivery of Mosquitos to 105 Sq, to quote two examples, but it certainly shouldn't be relied upon as a universal rule. For example, the squadron commander might be thought to have A, but would often simply choose whatever he fancied - or perhaps whichever was the best of the latest arrivals? A successful and favoured pilot might prefer to keep his "lucky" initial when moving from unit to unit.

Similarly the FAA would use ABCD, EFGH, and JKLM - for example with 880 Sq Sea Hurricanes. 880 also had a Z...but that was a special case!