[EV401]

You must go to your main iL-2 Folder.
It should look something like this: C:\Programfiles\Ubisoft\iL-2 Sturmovik 1946\MODS\STD\COM\MADDOX\iL2\Objetcs\air.ini.

If your are running Vista: C:\Programfiles(x-86)\Ubisoft\iL-2 Sturmovik 1946\MODS\STD\COM\MADDOX\iL2\Objetcs\air.ini.

Hope this help

Cheers!!