"Il-2 Sturmovik: 1946" originally began as an Eastern Front flight combat simulator which branched into Europe, The Pacific and then into the immediate Post-war Jet era. It has become a bit of a cult following with several loyal players continually playing, hosting, creating skins, missions and campaigns.
It is probably one of the longest running dedicated combat sims which though using a limited and dated engine, is still able to satisfyingly emulate the widest scope of aviation combat centered around World War 2 in varying difficulty levels and complexity. It has over 150 flyable aircraft from varying aspects of nearly all theaters of operations as well as associated maps. It includes pilot campaigns from nearly all sides, a quick mission builder and a full mission builder. But most of it's contemporary strengths come from beautifully made skins, missions, campaigns and utilities from it's many followers and fans that run the gamut of historical to flights of fantasy.
It's latest version is 4.12.2m (which is the latest steam version - No patching needed!) which has been officially updated by a group called Team Daidalos (rumor has it they are even working on 4.13!) has added flyable aircraft, tweaked graphics and sounds and additional mission building options and objects. (it even now has the option to add 3rd party "Online sounds" and still be a 'stock' game) It's multiplayer capability is via Hyperlobby where you can usually fly and/or host missions, join dedicated server maps, or get limited help from people there.
Besides the stock game, many have added one of the popular mods to add even more popular aircraft, different flight models, digitized sounds, improved graphics and mission building options and objects. (Most mods can be switched to stock easily via a simple program).
It has the added advantage of being able to run smoothly (A critical point in combat flight sims) on most older systems.
oh, I have purchased 2 retail box versions and the steam version so I've played a bit more than 10 minutes.. :)
(I have "Il-2:Cliffs of Dover" and "Il-2: Battle of Stalingrad" and I still
enjoy "Il-2 Sturmovik:1946)