I took a quick look at AH2 on my 1 GB P4-2.4 with Gf4-4200 running at 1024x768x32. Framerates were 40 or so with default settings.
The game took a long time to start. Can I suggest some sort of activity indicator?
The graphics looked really rough (default settings, remember). I too saw the invisible carrier.
The UI is simply appalling: the foldout concept looks nice but it covers far too much of the screen and the foldouts often go off-screen or cover something important (e.g. in the hangar). If you resize it down, the text can become unreadable. There is a standard tabbed dialog box most suitable for this and I suggest you use it.
Mouselook is excellent but needs to be automatically switched off when you bring the clipboard up.
I'll take another flight sometime soon and post further.