@ mav
Well you still have plenty of time to do all the unlocks since we won't start until Sunday. However, if you at least have the M.C. 202, Bf 109 E-3 and the Spitfire Mk.II, then that should allow you to play one side or the other for any of the missions.
Since you start the game with the E-3 and I'm almost certain you have a Spitfire Mk. IX that would only leave the 202 as the last unlock. To unlock the M.C. 202 simply complete the Invasion of Sicily, Single Mission; The Bait.
All the unlocks can be found in this thread:
http://forum.1cpublishing.eu/showthread.php?t=13167
@ StiC
Yeah, I was really looking forward to the Battle of the Bulge myself which was to follow the Korsun Pocket. However, all is not lost as if they make the Birds of Prey maps available as DLC for Birds of Steel as Anton has said is "
possible", then the Korsun, Bulge and Berlin historicals are certainly not out of the question.