Here we go:
http://code.google.com/p/il2coop/downloads/list
Simply unzip the archive somewhere below the user missions folder (e.g. "C:\Users\<your user name>\Documents\1C SoftClub\il-2 sturmovik cliffs of dover\missions\Multi\Co-Op"). Load the mission, start the battle and choose a army.
You are placed into a dummy aircraft. By default the dummys are some Blenheims and Heinkels without guns and fuel, just in case some idiots try to start a riot while waiting for the mission start

. If you like you can edit the IL2Coop.mis within the FMB to choose different aircraft types.
Now you can open the
mission order menu and select a mission. Use menu entry 8 or 9 to scroll the list.
After a mission was selected you can select an aircraft and position (pilot, gunner, ...). Again use menu entry 8 and 9 to scroll the list.
Now you can start the mission.
Client players only can select an aircraft and position.
Known issues:
- I'm not sure if it is working for clients already, there was no one around to test it

- Not all dummy aircrafts are destroyed when mission is started
- So far I didn't convert the group and aircraft names to more pretty text.
- The army selection doesn't influence the list of available aircrafts. This means you can choose RAF but can select a LW aircraft for the mission.
Source code of course in the archive but also available online here:
http://code.google.com/p/il2coop/sou...oop/IL2Coop.cs