Why does FSX crash at 100% loading, and how do I fix it?

Microsoft Flight Simulator X (FSX), including Steam Edition, usually crashes at 100% loading because scenery has finished loading, but aircraft, gauges, a weather file, AI traffic or the 3D view then fails to initialise. Test a new stock flight first; if every stock flight fails, rebuild FSX.cfg and repair the installation.

What does 100% loading mean in FSX and FSX:SE?

At 100%, FSX has completed the measured loading stages but has not finished creating a flyable scene. It must still initialise the selected aircraft, panel and gauges, apply weather, create traffic and open the rendered view.

The percentage alone cannot identify the bad component. The pattern of failure is much more useful:

Is FSX crashing or only stuck at 100%?

A closed FSX window, an application error or an entry in Windows Event Viewer indicates a crash; a progress window sitting at 100% may only be a long loading stall. Windows may briefly label FSX as not responding while it processes dense scenery or a complex aircraft.

Do not end the process immediately if disk or processor activity continues. If the flight eventually opens, diagnose it as a loading-performance problem using our checks for slow scenery, complex flights and add-on loading stalls rather than treating it as a crash.

How do I fix an FSX crash at 100%?

The fastest fix is to establish one clean stock flight and then change one variable per test. Do not begin by reinstalling everything; that destroys useful evidence and can leave the actual cause untouched.

1. Run a fresh stock flight: from the opening screen, create a new Free Flight with an untouched default aircraft such as the Cessna 172SP, an uncomplicated default airport, daytime, a simple static weather theme and traffic sliders at zero. Do not load the previous flight or a custom default flight.
2. Read the result correctly: if this flight opens, the core simulator can create a 3D scene. The fault is probably tied to the original aircraft, location, weather, traffic or saved flight. If selecting any Free Flight still causes the failure, follow our targeted Free Flight loading checks.
3. Separate aircraft from scenery: test the problem aircraft at the clean airport, then the stock aircraft at the problem airport. A crash in the first test points towards the aircraft; a crash in the second points towards the airport or surrounding scenery.
4. Isolate add-ons: disable the most recently installed aircraft, gauge, scenery, traffic, weather or utility package and restart FSX. Re-enable one item at a time. For a larger installation, our method for isolating faulty FSX add-ons by category avoids random deletion.
5. Check local scenery: disable the suspect area in the Scenery Library, restart the simulator and repeat the stock-aircraft test. Disable rather than delete it. A global mesh, texture or land-class package can affect every airport, not just the location named by its installer.
6. Remove traffic from the test: close external traffic programs and set AI, road, ship and leisure-boat traffic to zero. If the crash remains, temporarily disable the traffic package itself; a malformed traffic database can still be scanned even when its display slider is at zero.
7. Close weather and other live tools: stop external weather injectors, camera utilities, overlays and moving-map connections. These programs often connect just as the flight reaches 100%, so the timing can make an external failure look like a scenery problem.
8. Test memory pressure: restart FSX, choose a simpler aircraft and reduce texture resolution, autogen, scenery complexity and traffic. FSX remains a 32-bit application on 64-bit Windows. If only demanding aircraft-airport combinations fail, especially after a long session, address-space exhaustion is more likely than a corrupt stock file.

The stock-flight test is diagnostic, not merely a workaround. Once it succeeds, restore aircraft, airport, weather and traffic separately; changing all four at once puts you back at the start.

Can a weather file cause an FSX crash at 100%?

Yes. A saved FSX flight can use a companion .WX weather file, and a damaged weather file or missing referenced weather source can stop the flight after the progress counter reaches 100%.

Create a new flight with a static weather theme instead of reopening the saved one. If that works, back up the matching .FLT and .WX files from the Flight Simulator X Files folder in Documents, then recreate the flight. Do not set the damaged flight as the default again.

If fresh flights also fail after a weather change, close FSX and look in the active configuration folder for wxstationlist.bin. Rename it to wxstationlist.bin.old rather than deleting it; FSX normally creates a replacement station index. Restore the backup if this makes no difference. Never download a replacement weather file or DLL from an unverified source.

What should I check when only one add-on aircraft crashes?

A single-aircraft crash usually belongs to that aircraft's panel, gauges, model or configuration rather than FSX itself. Temporarily move its folder out of SimObjects\Airplanes, restart FSX and verify that the stock flight still loads.

Check that the add-on was installed for the correct edition and that its files are not buried one folder too deep. Older installers may target boxed FSX when FSX: Steam Edition is installed, while some gauges or startup modules are not compatible with FSX:SE. Repeat the add-on's installation steps only after confirming the correct simulator folder and required dependencies.

What if every stock flight crashes at 100%?

If every stock aircraft and default airport fails, reset FSX's per-user configuration and third-party startup modules before repairing or reinstalling the simulator.

1. Find the active configuration folder: boxed FSX normally uses %APPDATA%\Microsoft\FSX. Steam Edition may use %APPDATA%\Microsoft\FSX-SE or the FSX folder, particularly on systems that have also had boxed FSX installed. If both exist, identify the active one by checking which fsx.cfg changes when settings are saved.
2. Rebuild FSX.cfg: close FSX, rename fsx.cfg to fsx.cfg.old, then start FSX so it creates a clean configuration. File extensions may be hidden in Windows. Do not copy the whole old file back; reapply settings gradually and keep testing.
3. Disable startup modules: in the same folder, back up and temporarily rename dll.xml and exe.xml if present. If stock flights then work, restore the files individually and disable third-party entries until the responsible module is found.
4. Keep DirectX 10 Preview off: a clean configuration resets display options. If DirectX 10 Preview was not checked before, leave it unchecked during diagnosis; enabling it is not a fix. Also test without overlays, graphics injectors or post-processing utilities.
5. Repair core files: for FSX: Steam Edition, use Steam's installed-file verification. For boxed FSX, run the repair function from the matching installation media and include the same components, such as Acceleration, that belong to the installation. Verification can restore changed stock files but does not remove extra third-party files.
6. Retest before restoring anything: launch the same fresh stock flight with no external tools. If it works, restore one configuration file, module or add-on category at a time.

A complete reinstall is the last resort. FSX uninstallers can leave configuration files, saved flights and third-party content behind, so reinstalling over the same folders may reproduce the crash immediately.

How can I identify the exact file causing the crash?

Windows Event Viewer can identify the module in which fsx.exe stopped, although the named module is not always the original cause. Open Windows Logs, select Application and inspect the corresponding Application Error.

• A named third-party gauge, DLL or module makes the owning add-on the first item to disable.
• weather.dll makes saved weather, the companion .WX file and external weather injectors the first tests. It does not automatically mean that the stock DLL is damaged.
• terrain.dll or g3d.dll commonly points towards scenery, terrain data, graphics settings or memory pressure. Do not replace either DLL manually.
• ai_player.dll makes third-party AI aircraft and traffic databases the leading suspects.
• ntdll.dll is a generic crash location. It does not prove that Windows itself needs a replacement DLL.
• Exception code 0xc0000005 reports an invalid memory access, not the add-on or file that caused it.

I have already done that and it still crashes—what next?

If the stock-flight test, fresh configuration and file repair did not help, use the repeatable crash pattern and Event Viewer entry to choose the next test rather than repeating the same fixes.

• If the crash happens at every airport but stops with startup XML files disabled, restore their entries in small groups until it returns.
• If it follows one region even after its airport is disabled, test global mesh, land-class, texture and traffic packages that also cover that area.
• If it occurs only after a long flight or with dense scenery, restart FSX between tests and reduce memory-heavy settings; repairing files will not remove a 32-bit memory limit.
• If the entire computer restarts, freezes or shows a Windows stop error, treat that as a driver, hardware or operating-system problem rather than a damaged .FLT file.
• If FSX also crashes before the menu, during normal flight or under several unrelated conditions, use our broader FSX crash-diagnosis sequence for system-wide faults.

Keep each test reversible: rename files instead of deleting them, retain backups and change one variable at a time. That discipline is what turns an unexplained crash at 100% into a specific aircraft, weather, scenery, traffic, module or configuration fault.