FlightGear is an Open Source flight simulator created by a group of volunteers. The goal of the project is to create a sophisticated and open flight simulator framework for use in research or academic environments, pilot training, as an industry engineering tool, for DIY-ers to pursue their favorite interesting flight simulation idea, and last but certainly not least as a fun, realistic, and challenging desktop flight simulator. They are developing a sophisticated, open simulation framework that can be expanded and improved upon by anyone interested in contributing.It's also just a really fun flight simulator for anyone.Extra scenery and aircraft @ http://www.flightgear.org/download/.