The game runs fine with the software renderer, but with Direct3D renderer selected it can be very slow (several FPS per second). Obviously, you want to play with proper hardware acceleration, not with a fallback software option.

First of all, if you're new and just want to know how to get the most out of this sim, just install a Falcon BMS 4.34, a modern mod which is basically how this sim is played today.
You can get it on the official mod forum (might require registering, but it worth it,):
https://www.benchmarksims.org/forum/showthread.php?35505-Falcon-BMS-4-34-Full-Installer
and the update (read the installation instructions, it isn't obvious):
https://www.benchmarksims.org/forum/showthread.php?37763-Falcon-BMS-4-34-U1-Incremental-Installer

Ok, so if for some weird reason you want to fix vanilla Falcon 4.0 instead of using a modern mod, there's a tool called DXWnd, which can be used to get a much better experience with games designed for very old DirectX versions.

0. Disable any compatibility options you might have activated when tried to run it before
1. Download DXWnd: https://sourceforge.net/projects/dxwnd/
2. Extract somewhere
3. Run dxwnd.exe
4. Open your Falcon 4.0 folder (in Steam right-click the game and choose Manage -> Browse local files)
5. Drag and drop falcon4.exe into DXWnd window.
6. The configuration window will appear. Press OK for now.
7. Double click the Falcon4 in DXWnd. If it fails, run it through Steam and it should work in DXWnd after that.


That's it. You can go to options, select Direct3D and set the other options to the maximum.

After ensuring that it runs fine, you can tweak it in DXWnd a bit, to run it maximized (next section)

To open the configuration, right-click falcon4 icon in DXWnd and select "Modify"
Some recommended changes from default are:

Main tab:
No Banner
Hide desktop background
Keep aspect ratio
Desktop center (radio button)
Window initial position and size: select a 4:3 resolution with the height of your desktop resolution. For example width:1440, height: 1080. Other examples are 640×480, 800×600, 960×720, 1024×768, 1280×960, 1400×1050, 1440×1080, 1600×1200, 1856×1392, 1920×1440, and 2048×1536
Video tab:
Window style - modal
No taskbar overlap
...And press OK to save.

Questionable: hiding the taskbar. there's a checkbox for that too, but it only works if you launch DXWnd with admin rights, and it's kinda beta - it hides it and makes playing more immersive, but it won't return it to normal when you quit the game, requiring a restart or something. Maybe it'll be fixed in the next versions of DXWnd.
It can be set to auto-hide in Windows settings.

https://test-steamproxy.haloskins.io/sharedfiles/filedetails/?id=1945349685
https://test-steamproxy.haloskins.io/sharedfiles/filedetails/?id=1945349579