War Thunder is a new WWII-themed combat MMO in open beta. The developers plan on incorporating both ground based and naval warfare in later builds, but currently the only playable vehicles are aircraft. And while it is a beta and there are some issues such as the matchmaking (or lack-there-of), the user interface is fully functional and flight modeling for the aircraft is already pretty in-depth and detailed. You can fly with any level of difficulty, from arcade to full realism.

If you like flight sims I suggest you check it out, and if you're already playing let me know so we can squad up ( o3o) I could use some good wingmen to fly with in Historical Battles. Also I fraking love my Airacobra (\ ^3^)/