I'm sure you are all aware of IL2 Sturmovik 1946. It was introduced in 2006. It still has a huge following because they have a very creative mission and campaign editor. New players are still buying it and discovering all it's complexities.
Folks like me have created thousands of missions and campaigns not to mention custom skins by the thousands.
It has also been moded extensively with new maps, explosions, flyable planes, sound effects etc.
I hope that your product is as successful as IL2 or even more so. I highly recommend that you include very easy campaign, mission, skin and moding editors to make the game a classic.
I believe another reason for IL2 success is that you have the option of flying arcade style or as one of the most realistic flight simulators on the market.