[klem]

You should have a Control Panel for your GPU (video card). In there you should find profiles for each application/game that ATI have created. It will set the optimum Anti Aliasing, Anisotropic Filtering, etc etc for each game. Usually you can add a new one if ATI haven't provided one (just click Add and find the programme you want to make a profile for, in our case, Launcher.exe in the folder
C:\Program Files (x86)\Steam\steamapps\common\il-2 sturmovik cliffs of dover
Then you can set your own settings and Apply / Save.
It's a while since I saw an ATI Control Panel so have a look and try to make what I said fit.

If you don't have a profile it will simply use the default settings and again these should be visible in the Control Panel.