Fix FSX: Steam Edition startup crashes by isolating add-ons, rebuilding configuration files, checking the default flight and verifying Steam files.
FSX: Steam Edition usually crashes on startup because its configuration, default flight, scenery catalogue or an automatically loaded add-on has become invalid. First verify the Steam files, then rebuild FSX’s user configuration and test without third-party modules. The point of failure and Windows faulting-module name determine which fix to use.
What causes FSX: Steam Edition to crash on startup?
The most common causes are a damaged fsx.cfg, a bad saved flight, an incompatible module in dll.xml or exe.xml, and a broken scenery entry. Older DLL workarounds, mixed boxed and Steam installations, security software and missing legacy runtime components can also prevent FSX from reaching its main screen.
| Where FSX crashes | Most likely area to check |
|---|---|
| Before the splash screen | Steam files, permissions, security software, runtime components or graphics injectors |
| While the splash screen is visible | fsx.cfg, startup modules, dll.xml, exe.xml or scenery configuration |
| As the initial flight loads | Default flight, aircraft, gauges, weather or scenery used by that flight |
| After opening or changing menus | A local UIAutomationCore workaround or an add-on menu module |
Open Windows Reliability Monitor and inspect the failed fsx.exe event. A named add-on DLL is a strong lead; ntdll.dll or KERNELBASE.dll is usually only where Windows recorded the failure, not proof that Windows itself is damaged.
How do I fix an FSX Steam Edition startup crash?
Work through these checks in order and test FSX after every change. Stop when it starts reliably; changing several things together hides the actual cause.
- Back up your user files. Copy your FSX configuration folder, saved flights and any manually edited files before resetting them. Depending on whether boxed FSX has also been installed, Steam Edition may use an
FSXorFSX-SEfolder beneath%APPDATA%\Microsoft\. - Verify the Steam installation. Use Steam’s installed-files verification for Microsoft Flight Simulator X: Steam Edition. This restores missing or altered stock files, but it does not repair every add-on or necessarily remove files left behind by one. Back up intentional edits to stock aircraft or scenery files first.
- Rebuild
fsx.cfg. Close FSX, find the active configuration folder beneath%APPDATA%\Microsoft\, and renamefsx.cfgtofsx.cfg.old. FSX creates a clean file on its next launch. Display, realism and controller settings will return to defaults, but the old file remains available for reference. - Bypass the saved startup flight. If the crash occurs when the opening flight begins loading, temporarily move the user flight files out of the active Documents folder. Also test with
Logbook.BINrenamed if it exists; a damaged logbook can cause seemingly unrelated failures. Our guide to finding FSX Steam saved flights and logbook files covers redirected Documents folders and both common profile layouts. - Disable automatically loaded add-ons. In the same configuration folder, rename
dll.xmlandexe.xmlwith an.oldsuffix, then test again. These files start gauge modules and external utilities before or during launch. If FSX now works, restore the files and disable their entries in small groups until the offending product is identified. - Remove obsolete local DLL workarounds. Check the FSX installation directory for DLLs you knowingly added, especially an old local
UIAutomationCore.dllor graphics injector such as a third-partyd3d9.dll. Rename only user-added files for testing; never remove the Windows system copy. If Reliability Monitor names UIAutomationCore, follow our Steam-specific UIAutomationCore troubleshooting steps. - Test a clean scenery catalogue. Back up the active
scenery.cfgbeneath the relevant Microsoft folder in%PROGRAMDATA%, then let FSX build or use a clean default catalogue. If that fixes startup, restore custom scenery areas in small groups, checking that every path still exists. Disconnected drives and renamed scenery folders are frequent causes. - Check Windows compatibility and runtimes. Test FSX without forced legacy compatibility modes and with Steam and FSX running at the same privilege level. If an administrator test changes the result, correct the folder permissions rather than leaving Steam and FSX at mismatched elevation levels. Legacy DirectX or SimConnect components should come from the FSX/Steam installation or the add-on’s trusted installer, never from a random DLL bundle. For modern operating-system failures, use our Windows 10 and 11 checks for FSX configuration, permissions and legacy components.
How do I identify which FSX add-on is crashing?
The quickest reliable method is to establish a clean launch and then restore add-ons in controlled groups. Start with dll.xml and exe.xml modules, followed by the previous default aircraft and finally custom scenery.
If a category causes the crash, enable half its entries and test again. Repeat with the failing half until one module, aircraft or scenery area remains. For scenery, restore required libraries before airports that depend on them; a missing library can make a healthy airport appear to be the culprit.
A mistake we see constantly is copying an entire boxed-FSX configuration into Steam Edition. Add-ons may then point to the wrong installation, while similarly named FSX and FSX-SE profile folders make the problem harder to trace. Use file modification times to identify which folder the running simulator actually updates, and do not edit both blindly.
Should I reinstall FSX: Steam Edition?
Reinstallation should be the last step because a normal Steam reinstall can leave the faulty configuration, scenery catalogue and third-party files in place. If verified stock files still crash with a fresh fsx.cfg, no startup modules, a stock flight and default scenery, back up your content and remove the remaining add-on components before reinstalling.
When one product is responsible, remove that product rather than the whole simulator. Add-ons often place files in several locations, so use our procedure for removing every part of an FSX Steam add-on before testing the clean simulator again.