FlightGear

FlightGear is what you get when a flight simulator is treated as a public research project instead of a storefront. It models aircraft, weather, and a planet-sized scenery set, and it does that without a subscription or a scenery marketplace. The first hour is not a tutorial in the Microsoft Flight Simulator sense — it is closer to sitting down in a real cockpit binder and figuring out which switches matter.

The payoff is scope. You can fly a Cessna around a local field, line up an airliner on a Canvas glass cockpit, or join multiplayer traffic over published frequencies. Aircraft quality varies because the fleet is a community: some planes are museum pieces, others are the reason people stay. Worldwide scenery via TerraSync is large; plan disk space the way you would for any serious sim, not a casual download.

It is heavier than a browser flyer and more fiddly than a console racing game with wings. Joysticks help. Reading the wiki helps. If you wanted arcade dogfights, this is the wrong catalog page. If you wanted an open-source sim that still takes the physics seriously in 2026, it is one of the few that does.