Originally posted by RobG True, now that you mention it, the numbers stuck for some more than the names - I'd forgotten that the B17 was called the Flying Fortress, yet I'd tend to call the P51 a Mustang more than just a P51. I'm curious whether Americans tended to use the names or numbers more. I think the British used numbers for prototypes, but stuck with names and variants like the Spitfire Mk VII. In Australia, the Commonwealth Aircraft Factory had designations like the CA-17 (which was actually a Mustang built under license), but the names were used in practice as far as I know.
Pre-War the US used numbers. Occasionally a name would stick, but it was informal. I think members of the press gave the Flying Fortress moniker. The Brits gave all our planes names, and they had a pattern. Trainers named after schools - Oxford, Harvard etc. Bombers after cities - Blenheim, Lancaster, Manchester, Hudson etc. Fighters got more colorful and spirited names - Spitfire, Spiteful, Defiant etc. I think the observation planes got bird names a lot of the time - Albatross, Gannett, etc. I don't think the rules were really hard though, since we got planes like the Tiger Moth (and other moths in that series). There's got to be some history behind it all.
The Brits named the P-51 the Mustang (the A-36 verison the Apache). I think by the end of the war and certainly after we were giving planes official names. Not all of them stuck.