As realistic flight simulator the software is used for research, education, and for entertainment. As a 3D computer game, FlightGear has obtained a variety of features that go beyond the original objectives of flight simulators. This includes networking functions, multi-player mode on FligthGear servers, and multiple displays. Then there are large amounts of highly realistic and accurately modelled terrain data used to create a virtual reality through which you can fly.
FlightGear's sister project, TerraGear, is used for FlightGear's scenery generation. TerraGear is a software package for dynamically creating 3D models and maps from public GIS data such as DEM terrain grids, or NAOO land use data. It has special capabilities for constructing airports and runways from FAA data.
The virtual environment can include air traffic of planes controlled by the AI (Artificial Intelligence) component of the software. Random buildings and trees can be placed based on the terrain texture, and you can select between summer and winter textures.
At the core the FlightGear flight simulator software is the engine that simulates the physics that makes the airplanes fly. In in the real world, the motion of the aircraft is determined by the (simulated) forces between the air and the surfaces of the planes, as well as mass, gravity, and other physical properties. The environment simulation includes the sun, moon, and earth.
There are more than 400 aircraft and more than 80 different airlines with their distinct liveries (paintings). AI controlled aircraft and multiplayer aircraft can produce sounds like the main aircraft. Depending on the selected airport, FlightGear starts at different parking spots to match the size and type of the aircraft, and in some cases there is a visual guide leading you to the active runway along the correct taxiways.
The software includes a highly realistic weather simulation module that simulates the interaction of the atmosphere with the terrain. You can make weather from downloaded or custom made METAR weather reports and experience for example the interesting effects of weather phenomena occurring between different meteorological systems. This includes thermals (localized upward air flow due to high surface temperatures), cloud formation at mountains due rising and cooling air, cold fronts leading to precipitation and fog layers, etc.
Since the FlightGear software is open source, anybody can get a copy of the source code and make modifications for specific applications. This has allowed researchers and engineers to use it for a variety of educational, entertainment, and training projects. The software can be used to simulate random system failures and is used various FAA approved flight simulators.
The software is available as source code and in binaries for all common platforms. Many Linux distros offer convenient installation options through their software repositories. Ubuntu and distributions based on Ubuntu can install FlightGear through GetDeb from the PlayDeb web site.
A commercial closed source alternative to FlightGear is X-Plane. It is one of the most advanced flight simulator software packages for personal computers and includes complete scenery of the planets Earth and Mars. Like FlightGear, X-Plane creates a realistic flight model by computing the forces that act upon each part of the aircraft. This includes turbulence, ground effect, and downdraft simulations.
For more information, download and installation instruction for FlightGear see the project web site.
If you are more into driving than flying, the TORCS based car simulators for Linux are the way to go.