How do I fix FSX 'Unable to load some files'?

The FSX “Unable to load some files” error usually means Microsoft Flight Simulator X has a missing, damaged or mismatched program file. For FSX: Steam Edition, verify the installed files; for boxed FSX, run the original installer’s Repair option. If it persists, disable start-up add-ons and rebuild FSX’s user configuration.

What does the FSX error mean?

The message is a program-file integrity error rather than a normal aircraft or scenery warning. Its full wording may say that Flight Simulator was unable to load some program files and will now exit, followed by a request to repair or reinstall the simulator.

Common causes include antivirus quarantine, an interrupted update, an add-on that replaced a default DLL, mixed service-pack files, or files copied from another FSX edition. If the warning names one particular add-on, aircraft or scenery file, reinstall that product first instead of repairing the whole simulator.

Which FSX repair should I use?

Choose the repair method that matches your edition; boxed service packs and Steam file verification are not interchangeable.

Fix the unable-to-load-files error step by step

1. Close FSX and preserve your custom content. Back up the active FSX configuration folder and any aircraft, scenery or other files you knowingly installed. Do not back up and later restore unknown DLLs from the simulator’s main directory, because one of them may be the fault.
2. Check antivirus quarantine. Look for an FSX or add-on file removed at the time the error began. Restore a file only when you recognise its source and path, then verify or repair FSX so that an authentic copy replaces it. Avoid downloading individual DLL files from unrelated sources.
3. Verify FSX: Steam Edition. In the Steam library, open FSX’s Properties, select Installed Files, and run Verify integrity of game files. Start FSX once before reinstalling any add-ons. Verification replaces missing or altered default files, but it may leave additional third-party files in place.
4. Repair boxed FSX from its original media. Run the installer with administrator rights and select Repair where offered. Use media and updates intended for the same FSX edition and language. Our boxed FSX repair and service-pack guidance explains the correct recovery sequence and the differences between base FSX, service packs, Acceleration and Steam Edition.
5. Generate a clean user configuration. Press Windows key plus R, enter %APPDATA%\Microsoft, and rename the active FSX folder to FSX.old. Steam may use FSX-SE when another FSX installation is also present. FSX will create a clean folder at its next start, temporarily removing old fsx.cfg, dll.xml and exe.xml settings from the test.
6. Remove the most recent add-on. If verification succeeds but the error remains, uninstall any module, weather engine, aircraft utility or scenery tool added just before the failure. Use its uninstaller where possible; deleting DLLs at random can create a second missing-file problem. If FSX works with the clean configuration, re-enable start-up modules individually rather than copying the entire old folder back.
7. Correct an invalid boxed-FSX installation path. When Repair claims FSX is not installed, opens the wrong installation or asks for files in an obsolete location, use our steps for repairing the FSX registry path before attempting another repair.
8. Perform a clean reinstall only as the final step. Uninstall FSX, preserve your personal content, and rename the remaining installation directory so that stale third-party files cannot be reused. Reinstall the simulator, launch it in its clean state, and then restore updates and add-ons in stages. If the installer or accompanying alert specifically names MSXML, follow the MSXML 4 repair procedure for FSX instead of repeatedly reinstalling the simulator.

Will verifying or repairing FSX remove add-ons?

Verification or Repair can replace edited default files, but it does not reliably remove extra files installed by add-ons. This is why the error can survive a successful Steam verification: an incompatible third-party DLL may still be present and referenced by dll.xml or exe.xml.

Back up custom content first, but restore it selectively. Copying the complete old FSX directory or configuration folder over a clean installation often restores the exact fault that caused the error.

Why does the error return after repair?

A returning error usually identifies when the damaged or incompatible file is being reintroduced.

• If it returns immediately on a clean installation, check security software and confirm that the installer, language and update path match the FSX edition.
• If it returns after restoring the old configuration folder, suspect a start-up module listed in dll.xml or exe.xml.
• If it returns after one add-on is installed, remove that add-on and repair or verify FSX again; it may have replaced a default file.
• If the original warning disappears but FSX then closes with a different crash, use our structured FSX crash-isolation process rather than repeating the same file repair.