So you can install the program on your PC and use it without ever needing to connect?
I'm not too sure .....
Also the term 'simulator' may be not as accurate as 'game'. For insrtan ce you would not call 'Lock on' a simulator. At least I wouldn't. To be a 'flight simulator' the 'game' or program should be adjustable to the extent that it will fairly realistically simulate the real life experience of flying an aircraft. I'm not sure this is known yet.
Regarding being able to play offline, Microsoft published this new item back in January...stating that you can play online or offline:
http://www.microsoft.com/games/flight/#news3In this article, they state that they are not making an arcade game, but continue to discuss the "flight simulation experience." This could be debatable whether to call it a game or a simulator, but it is known that Flight will probably have an SDK, as there was an Ad of some sort that Microsoft published a while back where they were looking for a lead developer to take on the Flight SDK.
http://www.microsoft.com/games/flight/#news2