However, Steam has not stated which regions the game is currently available for, and it is definitely available for the US. If the game is not available for your region, you can always download it and play the free content from the MS Flight official website.
When some users try to access the game page from outside of the US, they see this:
If you are lucky enough to be able to play the version that’s just made its way to Steam, you will also get better prices on Microsoft’s Flight premium downloadable content than were previously available via Xbox.com.
The Steam edition is different to the original Microsoft Flight version in that it provides better pricing via the Hawaiian Starter Bundle, which is cheaper on Steam by $13 than it is on the Xbox.com Marketplace. The bundle includes two aircraft, the Maule M-7-260C and the North American P-51 Mustang, and the Hawaiian Adventure itself. Note that theoffers free preview versions both for the North American P-51 Mustang and for the Maule M-7-260C.