Just thought it's worth mentioning that the Combat Demo of the game is completely offline and you don't need to buy anything to try it out.
It isn't available directly from the site, but you can find it with some searching. In fact, this tool appears to download it from the official CDN. (Never used that script; It seems Frontier is tolerating its use.)
The demo is quite limited but it gives a good idea of the flight mechanics, how the game looks and of the system requirements.
