As said, you will need CFS3 to play OFF, but it is well worth the experience. Depending on the realism level you choose, you can die every mission or last several months. You can create an almost unlimited number of pilots, flying for either side and select any of the times throughout the war as well as any of the squadrons/Jastas. All squadrons have historical accuracy as to the types of a/c and the skins as well as names of squadron members at the given time.
I can assure you, at 100% realism, you'll be more worried about saving your own hide! The graphics are great, one of the best overall sims I've ever seen. One of the toughest, too!!! If you are up to the challenge......