I have already said this in a reply to another poster with the same problem. I do so a second time, marking it as a "question/problem" in the hope of encouraging a response - which the other poster has not been granted.

After launcing the game, there is no response from the PC whatsoever, for at least three minutes. But then up does pop the title screen - at 50% loading complete! And there it sits. Though it does continue past 50% if you wait, for a, quite frankly, unnacceptable amount of time (at least 10 minutes). Then the old sepia effect video cuts in. <Esc> to exit does nothing. All keyboard controls and mouse controls are kaput. If you try <alt-tab> the game just crashes outright. I has not done that on any of my older PCs in the past, and loaded quickly on those older PCs.
No <alt-tab> means I can no longer review the aircraft guide whilst in mid-play anymore.
I've owned copies of "IL2" since 2001, and owned this GOG version since 2013. I periodically keep coming back for more. But this time no dice whatesoever, it now seems a completely broken product.

Most likely this is "updates" for "Windows 10 compatability" kaiboshing us Windows 8.1 users.
Last time I tried IL2 it was on a Windows 10 system, but much, MUCH lower spec than the Win8.1 system I am now trying to run it upon. And before it's suggested - no, I no longer have access to said Win10 system. And also no, I do not wish to pay to upgrade to an OS I detest.

Anyway the system I'm trying IL2 on now is an Acer Predator G3-605 with Win 8.1. Still holds it own despite being a 2014 model, though the Nvidia GeForce GTX745 leaves a lot to be desired. However should run IL2 with no issues. Full system specs are viewable online.

thank you, at least someone else here is having the same issue, if this is ever going to get fixed we need to do something about it because GOG will not

Here is what I did to make it work on Win10. Not the best solution but it does work. This is for the GOG version with standalone installer. I don't know if it will work on any other version:

1. This will be a fresh install of IL-2 1946
2. Right click the setup.exe and select "run as admin" and select to run in compatibility mode for "Win XP (SP2)" and then run the installer
3. Navigate to the install folder
4. Set both il2fb.exe and il2set.exe to run as admin. (I didn't use any compatibility modes but you can experiment)
5. Open il2set.exe and set provider to OpenGL & Windowed (This is essential!), & disable intro and stencil buffer
6. In the video tab uncheck all boxes (Once you are up an running you can come back here and experiment with these options)
7. In the install folder you can open config.ini with Notepad and set a custom resolution under "[window]" and then save

Note: I set mine to my desktop resolution of 3840x2160 and the game auto scales the window to 3840x2127. This also means that you will have a title bar at the top of the screen. :( For some reason the game does not want to run properly in full screen mode, and doing so results in that system bog down and eventual CTD. The interesting thing is that the graphics engine and GUI will still correctly scale to 4k without any additional setup.

8. Lunch the game. The initial run of the game will take some time but subsequent startups should be faster. You should almost instantly get the loading screen after you've run the game once already.
9. If you cant use the cursor at the main menu, WinKey to desktop and then reselect the game window and it should work again

Note 2: If you are using a monitor with a display port connection or have multiple monitors connected try the community made patch: https (colon) //www (dot) sas1946 (dot) com/main/index.php?topic=57243.0