This "Strike Fighters" flight sim series dates back to around 2002 and was last updated in 2013.
The Strike Fighters series covers the cold war era in several historical+fictional scenarios, with a lots of flyable aircraft from the P-51D Mustang to the F-15 Eagle. It is reasonably easy to learn, for a flight sim.
Since 2013 the developer switched to mobile flight games, AFAIK since the market for the PC game was unfavourable. It is unfortunate since the game was fun, extremely mod friendly and also DRM free.
The developer currently runs a fundraiser for a Windows 10 update for the PC game series. It is here:

Help fund the Strike Fighters 2 Windows 10 update!

Strike Fighters 2 is a series of popular PC games we released back in 2008 (over 11 years ago!). It was a unique series of inter-connected light/casual flight simulation games set in the Cold War. Despite its age, it's still being enjoyed by many users, thanks largely to its huge and active mod community.

The games were originally designed on (then brand new) Windows Vista, but over the years, new Windows versions have came and gone (Windows 7, 8, 8.1, and finally 10), the hardware has evolved at dizzying speed, and internet security and privacy have become major concerns. With all these changes, some people are reporting issues running our old games on newer machines.

We'd love to be able to update the series to the latest Windows and Direct X version. But we're a very small independent company with very limited resources, and we do not currently have the funds to do this. And this is where you can help!