War Story, Goshawk Squadron, and one more whose title I can't remember, all about WWI. I think they have just been republished - bound to be on Amazon.
Also, A Good Clean Fight about the WWII desert war.
In a similar vein I loved Len Deighton's Fighter, although various people no doubt more knowledgeable than me have slagged it off.
If this all keeps up we are going to need a Books forum!