I'll probably get slapped for this, but WTHYOLO. Apologies in advance to HTC, I mean no disrespect by posting this.
I'll start by saying that HTC has their terrain designer tool, and that might be a good place to start since you'll see a glimpse of what has to go into a project like Aces High, at least in the terrain department.
Also, Sick and a few other gamers have started a company called targetware, and their project has a big emphasis on player created content including 3D aircraft modelling, artwork, skins, terrain, sounds, you name it. Drop them a note (beta application available at
www.targetware.net) if you want to try your hand at some of this stuff. At the very least, their preliminary 3d model and skin design specs (available to anyone interested, not just the beta team) can give you an idea of what kind of things a game developer needs from a game production quality aircraft model.
Again, I mean no disrespect to HTC by putting this information in this thread in this forum, because the thread seemed to lead directly to it. I won't be upset if you guys (HTC admins) need to delete it, but I hope you won't ban me from the forums

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eagl <squealing Pigs> BYA
Oink Oink To War!!!