I tried to install the game on my PC running Windows 8.1, but the game crashed (I'll post the error code later) and with all the effort I made into trying to launch the game, I had no success.
However, I installed the game on my parent's PC today running Windows 7 and it works just fine.
Both were fresh installs, with no traces of previous Microsoft Flight installations, both were installed through Steam using the same Steam account. Other GFWL games work fine on both PCs. Both systems are x64 and Professional edition. The only difference is that Windows 7 is in Polish language and Windows 8.1 is in English.
If anyone have more info about this issue or about Windows 8.1 compatibility (though I think I saw stories of successfully launching the game on Windows 8.1 posted in the Internet), let me know and/or update the article accrdingly :).