Looking at the most recognizable ones at least, I was wondering why the older starfighters of the Rebel Alliance are called X-Wing, Y-Wing, and the newer ones A-Wing and B-Wing. A logical order would be to name the first model A-Wing and so on.
Is there any system or structure supporting the ship naming scheme, or is this just coincidence/will of Mr. Lucas ? Or is it because you could say the ship's shape corresponds somewhat to those letters (even the B-Wing does, albeit remotely). AFAIK, these four examples do not share one manufacturer, which adds another dimension to the question.
BTW, this question is interestingly related.