The current version is known as IL2 Sturmovik 1946. The original IL2 came out with a few Russian and German planes, they developed the game with expansion packs (added more maps and US / UK planes etc) and last year released 1946, which has all prior versions plus more.
We have an online server on Inspire (they are the ones who provide the Flight Sim server) and on that run the current public release version 4.08m. This server runs 24/7 and is to team up with players and conduct missions that involve dogfights and bombing missions (one teams mission may be to bomb a harbour with some bombers and others providing fighter escort - the other team is defence). Mate against mate stuff.
We use the soon to be publically released version 4.09m for co-op missions. Here you fly with team mates, all on one side with AI planes making up the rest of your squadrons (so you can give AI planes commands, like to fly in formation, break, attack etc), against an AI enemy.
As above, head over to
http://kiwisim.net.nz/ and click the Forum Link / IL2 forum for more info. We are a dedicated bunch of guys who fly most nights of the week. At least twice a week someone will host a co op mission and we'll team up, learning skills on a per plane basis.
It's a steep learning curve, you can play it in 'arcade mode' in single player but online servers use more sophisticated settings, such as engine management, torque and blackout effects, locked cockpits at times and so on. It took me a while just to be able to take off and land without breaking the plane.
Unfortunately IL2 1946 is becoming hard to find, you can get the original IL2 Sturmovik in $10 bins but it's really for off line play only now as no servers are about.