Realistic Flight SimLooking for a truly high-quality flight simulator that also happens to be free? Well, search no longer because you’ve just discovered FlightGear!With FlightGear you get an open source flight simulator that is in many ways right up there with its expensive commercial counterparts, such as Microsoft’s Flight Simulator.

FlightGear is definitely no slouch when it comes to recreating the flying experience and you might be surprised by its attention to detail and commitment to realism. It’s also one of the few simulators out there that will run on almost every major OS platform (Windows, Linux, Mac, UNIX), and it doesn’t even demand bleeding edge hardware to run well either.

All in all, FlightGear is a feature-packed, top-tier simulator that just might bring out the ace pilot in you. Be sure to download it take your favorite bird up for a few test flights.
Official Features List:

Over 20,000 real world airports included in the full scenery set.
Accurate runway markings and placement, correct runway and approach lighting.
Taxiways available for many larger airports
Sloping runways (runways change elevation like they usually do in real life.)
Accurate terrain worldwide, based on the most recently released SRTM terrain data.)
Scenery includes all vmap0 lakes, rivers, roads, railroads, cities, towns, land cover, etc.
Nice scenery night lighting with ground lighting concentrated in urban areas (based on real maps) and headlights visible on major highways. This allows for realistic night VFR flying with the ability to spot towns and cities and follow roads.