Flightgear is an open-source, multi-platform flight simulator.
The FlightGear flight simulator project is an open-source, multi-platform, cooperative flight simulator development project. Source code for the entire project is available and licensed under the GNU General Public License.
The goal of the FlightGear project is to create a sophisticated flight simulator framework for use in research or academic environments, for the development and pursuit of other interesting flight simulation ideas, and as an end-user application. FlightGear developing a sophisticated, open simulation framework that can be expanded and improved upon by anyone interested in contributing.
There are many exciting possibilities for an open, free flight sim. FlightGear hope that this project will be interesting and useful to many people in many areas.
Download FlightGear from http://www.flightgear.org/download/
For more information please visit http://www.flightgear.org/