Some quick notes on the film viewer.
START > PROGRAMS > Aces High II > Aces High II Film Viewer. Or launch it directly from your game install (C:\Programs\HTC\Aces High II\ahfilm.exe).
After the first time running it, AHF files are automatically associated with the viewer and you can double click a film to open it. One side note though: You cannot start the viewer while the game is open.
To view the films, I usually do so in External View, with Trails, Icons and Recorded Views checked. This gives you a good overview of what happened and who pulled which move. Switching to Internal will give you an idea on how a certain move looks from the inside of the cockpit. Note that you can adjust your head positions in the viewer just like you do in game (arrow keys, page up/down, F10 to save) and that you can also (if youre not using recorded views) use the numpad to look around.
Double clicking a name on the list to the right will let you view the film from another planes point of view. Sometimes its useful to go to the opponents plane and watch yourself flying, how it looked from his point of view. Dont use recorded views if you do that, as those are always *your* views (where you looked to), not the opponents.
Filming and reviewing your fights can be a great learning tool - sometimes the "miracle cheat move" the opponent pulled on you is a simple thing and you can do it yourself next time.
You can also record your own films in game. ALT_R starts/ends recording. While film is capturing, you can see a red R in the upper left corner of your screen. The films are saved as film##.ahf file in your games film folder (C:\Programs\HTC\Aces High II\Films\).
