My guess is that Aces High, or the graphics card, isn't loading the windscreen texture properly, or can't deal with the transparency information, or something along those lines, and is displaying the windscreen as a solid polygon. The older aircraft models have untextured windscreens that look like empty holes, whereas the RV8's windsreen has reflections, and it reacts to the sunlight (it looks a bit like the windscreen from Falcon 4.0).
Perhaps Hitech are modelling the windscreens to a different standard than before, which would impact the RV8, the new Corsairs, and subsequent models. Presumably the gentleman doesn't have a problem with the C-model Corsair, which is unchanged from before.