X-Plane
X-Plane is pre-made with several commercial and military aircraft and global scenery. It covers most of the Earth. X-Plane has a plugin architecture that allows users to create their modules. It also increases the software's functionality by letting users create their worlds or other places on Earth. There is also an X-Plane forum. The forums are where users can share aircraft, scenery, plugins, and the Scenery Gateway website, which allows users to share airports with other users, which can be installed into the base product.