FlightGear is the best free alternative to Microsoft Flight Simulator: an open-source simulator with a genuine flight dynamics engine, global scenery, weather, multiplayer and a large free aircraft library, on Windows, macOS and Linux. Visual fidelity is well behind MSFS; system depth is not.
Serious flight simulation is expensive twice over: the simulator, then the aircraft and scenery add-ons. There is one free simulator with genuine depth, and it has been flying since before Microsoft's current series existed.

FlightGear is a full civilian flight simulator with a real flight dynamics engine, worldwide scenery, weather, a large aircraft library and multiplayer. Aircraft systems are modelled deeply enough that checklists and procedures matter.
How it differs from Microsoft Flight Simulator: Scenery and cockpit art do not approach modern MSFS, which leans on satellite photogrammetry and streaming. FlightGear's quality varies by aircraft because they are community-contributed — some are studied to switch level, others are rough.
| Game | Genre | Size | Licence | Platforms |
|---|---|---|---|---|
| FlightGear | Simulation | 2.0 GB | Open Source (GPL-2.0) | Windows, macOS, Linux |
FlightGear is a full civilian flight simulator with a real flight dynamics engine, worldwide scenery, weather, a large aircraft library and multiplayer. Aircraft systems are modelled deeply enough that checklists and procedures matter.
The difference: Scenery and cockpit art do not approach modern MSFS, which leans on satellite photogrammetry and streaming. FlightGear's quality varies by aircraft because they are community-contributed — some are studied to switch level, others are rough.
FlightGear clears all five: genuinely free, complete enough to fly worldwide, still maintained, serious enough to recommend against paid sims, and high quality for anyone who wants simulation rather than an arcade flyer.
FlightGear is the best free alternative to Microsoft Flight Simulator: an open-source simulator with a genuine flight dynamics engine, global scenery, weather, multiplayer and a large free aircraft library, on Windows, macOS and Linux. Visual fidelity is well behind MSFS; system depth is not.
Yes. Every game listed here is free with no trial, no paywalled content and no pay-to-win purchases. Each has been assessed against PlayBound's five published criteria — including high quality only.
No. None of these games charge for multiplayer. Public servers are community-run and free to join, and there is no subscription of any kind.
Scenery and cockpit art do not approach modern MSFS, which leans on satellite photogrammetry and streaming. FlightGear's quality varies by aircraft because they are community-contributed — some are studied to switch level, others are rough.
Every game here has been assessed against the PlayBound Bar — five published criteria for whether a free game is actually worth your time.