Why won't FSX launch, and how can I fix it?

Microsoft Flight Simulator X (FSX) usually fails to launch because a background fsx.exe process is stuck, its configuration or logbook is corrupt, an add-on is loading through dll.xml or exe.xml, or a legacy runtime is missing. End the process, reset user files, test without add-ons, verify or repair the installation, then diagnose the exact error.

What does the FSX launch symptom mean?

The point at which FSX stops usually identifies the right repair.

How do I fix FSX not launching?

Use these checks in order, testing FSX after every change so that you know which action solved the problem.

1. End any stuck FSX process. Open Task Manager, look under both Processes and Details for fsx.exe, and end it if present. Restart Windows if it returns or cannot be closed. For FSX: Steam Edition, restart the Steam client as well.
2. Rebuild the FSX configuration. Press Windows key and R, enter %APPDATA%\Microsoft, then open the FSX folder. A side-by-side boxed and Steam installation may instead use an FSX-SE folder. Rename fsx.cfg to fsx.cfg.old; FSX will create a clean file on its next successful launch. Our clean FSX first-launch checks explain how to establish a stock baseline before restoring settings.
3. Stop add-ons loading at startup. In the same user folder, rename dll.xml and exe.xml by adding .old to each name. These files start modules such as weather engines, menu extensions and external utilities before the main interface appears. If FSX now opens, restore one file and then individual add-on entries until the failure returns.
4. Test the logbook. Open the Flight Simulator X Files folder in Documents and rename Logbook.BIN to Logbook.BIN.old. Check the OneDrive Documents location if Windows redirects that folder. A corrupt logbook can leave FSX hanging at its splash screen; use our targeted logbook recovery utility if you want to attempt to preserve its entries.
5. Verify or repair the core installation. For FSX: Steam Edition, use Steam's Verify integrity command in the game's properties. For boxed FSX, run the repair option from the original installer, then restore the service-pack or Acceleration state appropriate to that edition. Verification repairs core files, but it does not normally replace a corrupt per-user fsx.cfg.
6. Repair the named dependency. FSX and older add-ons can require legacy DirectX components, SimConnect versions, Microsoft Visual C++ runtimes and MSXML. Use the prerequisite installers supplied with FSX or the affected add-on rather than downloading individual DLL files. If the message specifically names MSXML 4, follow our MSXML component repair procedure.
7. Check security and compatibility settings. Restore a quarantined file only when you recognise and trust it. Run FSX as administrator once as a diagnostic; if that fixes it, correct the installation-folder permissions rather than relying automatically on permanent elevation. With Steam Edition, avoid running Steam and FSX at different privilege levels. Remove blanket Windows compatibility settings while testing unless a particular boxed installation requires them.
8. Read the Windows fault record. Open Event Viewer, select Windows Logs and then Application, and inspect the error recorded at the launch time. A module bearing an add-on's name points directly to that add-on. Generic modules such as ntdll.dll or KERNELBASE.dll do not identify the cause by themselves, so continue with configuration and add-on isolation.

What if FSX starts after renaming fsx.cfg?

A successful launch with a new fsx.cfg means the simulator installation itself is probably sound. Reconfigure display, sound and controller options manually instead of immediately copying the old file back, which would also restore the bad setting.

If the problem returns after changing one option, reset that option first. Display mode, an unsuitable resolution, DirectX 10 Preview and controller assignments are common areas to check. Keep the old configuration temporarily for reference, but do not merge unknown sections wholesale.

What if an add-on stops FSX from opening?

An add-on that loads a DLL, starts an external program or installs a complex gauge can close FSX before the menu appears. Aircraft may also cause trouble when their folders contain malformed configuration files or incompatible gauges.

Remove the most recently installed add-on first. If several were installed together, restore them individually and launch FSX after each one. Steam Edition users should also check the common FSX add-on compatibility and SimConnect traps, especially for installers designed around boxed FSX folder and registry locations.

Does a splash-screen hang mean the scenery is broken?

A hang before the main menu is more often caused by the logbook, configuration or an automatically loaded module. Scenery becomes the stronger suspect when FSX reaches the menu but stops while loading a selected flight. In that case, disable the latest scenery entry rather than deleting the entire scenery library.

Should I reinstall FSX?

Reinstallation is the last step because uninstalling FSX may leave its user configuration, logbook and add-on files behind. Reinstalling over those same files can reproduce the original launch failure.

If verification or repair fails, back up saved flights and personal add-ons, uninstall FSX, rename the remaining installation and user-configuration folders, and install a clean copy. Launch a stock aircraft at a default airport before adding service packs, Acceleration or third-party content. If that clean copy works, restore add-ons one at a time rather than copying the old installation back in one batch.