If you intend to use X-Plane in an area with no internet access, always run X-Plane immediately before going offline. The download version of X-Plane regularly contacts its license server but will not be disabled for at least two weeks after the last internet contact. After about 2 weeks you may find that X-plane is temporarily locked until you once again regain an internet connection.
If you are likely to be offline for long periods, rather purchase the 12 DVD set – available here. This version does not “phone home”.