your air.ini file will be in:
C:\**YOUR IL21946FOLDER**\MODS\STD\com\maddox\il2\objects
as to what it does . . . . ?? to be honest I'm not sure, it looks like a reference file for aircraft access on maps/load ups but I'm afraid I cant give you a definite answer on that one :?
Are you installing the new aircraft one at a time, making sure each new one works before you add the files for the next?
If you have the space (or a USb hard drive perhaps?) I'd recommend keeping a copy of your Il2 modded install separately, I back up my whole installation before each new MOD I add so if it doesn't work or narks my install I can just delete and copyn'paste the backup straight over.
Are you using Vista by the way? if so there are a couple of tweaks which can make life easier.
Thank you Tiger88 looks like the unified installer includes 4.09 and that switcher is the cats meow
S~
smoothader