Fix an FSX multiplayer Visual C++ runtime error by isolating add-ons, checking the faulting module, repairing x86 runtimes and verifying FSX files.
A Visual C++ Runtime Error in FSX multiplayer is usually a local FSX or add-on crash, not a server fault. Test with a default aircraft and no multiplayer add-ons, identify the faulting module, then repair the required 32-bit Visual C++ runtime or the add-on responsible. FSX: Steam Edition users should also verify game files.
Is multiplayer actually causing the runtime error?
First establish whether FSX crashes because multiplayer was opened or because joining loads a particular aircraft, gauge or client module.
- Repeat the flight offline. Use the same aircraft, airport and weather. If the runtime error also occurs offline, troubleshoot the aircraft or FSX installation rather than the network.
- Create a stock multiplayer test. Both players should use the same FSX edition and update level, a default Cessna 172, a stock airport and a simple weather preset. Leave shared cockpit disabled.
- Remove optional modules. Exit add-on weather, traffic, camera, overlay and voice tools. If an external multiplayer client is required for the connection, keep only that client active.
- Change one item at a time. Restore the normal aircraft, shared cockpit and other add-ons separately. The first item that brings the error back is the likely trigger.
| When FSX fails | Likely area | Best next test |
|---|---|---|
| Offline and in multiplayer | Aircraft, gauge, core file or runtime | Use a default aircraft and inspect the faulting module |
| Only after joining one session | Aircraft substitution, shared cockpit or version mismatch | Ask the host to select a default aircraft |
| Only when an external client starts | Client plug-in or its dependency | Disable other modules and reinstall that client |
| No crash, only a timeout or disconnect | Network, firewall, NAT or host configuration | Use our FSX multiplayer connection checks |
Boxed FSX and FSX: Steam Edition do not use the same native lobby system and should not be treated as interchangeable clients. The original GameSpy public lobby for boxed FSX is defunct; repairing Visual C++ will not restore it. Boxed users must use an available LAN, direct-IP or separately installed multiplayer method.
What does the faulting module tell you?
The faulting module usually determines whether to repair Visual C++, reinstall an add-on or investigate FSX itself.
After the crash, open Windows Reliability Monitor or Event Viewer and find the Application Error recorded at the same time as the fsx.exe failure. Record the faulting module name and exception details before changing anything.
- An add-on DLL or gauge is named: disable or reinstall the aircraft, gauge or client that supplied it. Make sure its installer supports the exact FSX edition being used.
msvcr*.dllorvcruntime*.dllis named: repair the matching x86 runtime, but keep testing add-ons. A faulty gauge can crash inside a healthy runtime library.- An activation-context or side-by-side error appears: follow our x86 Visual C++ and legacy SimConnect repair procedure.
fsx.exe,ntdll.dllorKERNELBASE.dllis named: the entry is inconclusive. Use the stock-aircraft test and our structured FSX add-on isolation process.
How do I repair the Visual C++ runtime for FSX?
Repair the required x86 runtime rather than installing only the newest or 64-bit package.
- Back up customised files. Save altered panels, gauges, configuration files and default aircraft files before repairing FSX.
- Repair installed x86 packages. In the Windows installed-apps list, select Repair for the relevant Microsoft Visual C++ Redistributable where that option is offered. FSX is a 32-bit application, even on 64-bit Windows, so an x64 package does not replace the x86 package.
- Use the matching installer. If Windows offers no repair option, rerun the trusted x86 redistributable installer supplied with FSX or the implicated add-on. Different add-ons can require different runtime generations, so installing only the latest package is not a complete fix.
- Repair the simulator files. In FSX: Steam Edition, use Steam's file-integrity verification. For boxed FSX, run the repair option from the original media and restore the same official update path used previously. Acceleration includes SP2-level core updates, so do not install the separate SP2 package over Acceleration.
- Reinstall the implicated add-on. Use an installer intended for your edition of FSX, then test before restoring other modules.
Do not uninstall every Visual C++ package: several versions are designed to coexist and may be required by other programmes. Never download a loose runtime DLL, copy one from another computer or place one manually beside fsx.exe.
Will reinstalling FSX fix the error?
A full reinstall often fails because it can leave roaming configuration files and third-party modules behind.
Before uninstalling, open %APPDATA%\Microsoft and back up the active FSX configuration folder. Depending on whether boxed FSX and Steam Edition coexist, it may be named FSX or FSX-SE, and the configuration file may be fsx.cfg or fsx_se.cfg.
- Regenerate the configuration. Rename the active configuration file with a
.baksuffix and let FSX create a clean one. - Disable automatic loaders. If present, temporarily rename
dll.xmlandexe.xml. These files start add-on modules and external programmes that file verification may not remove. - Test a stock session. If it works, restore one loader entry or add-on at a time rather than copying the entire old configuration back.
Steam verification can replace modified stock files, but it does not necessarily delete extra files installed by third-party add-ons. That is why a clean configuration and module test is more useful than repeatedly verifying the same installation.
Why does FSX fail only when joining one session?
A session-specific crash usually points to the host's selected aircraft, shared-cockpit systems or a local aircraft substitution rather than Visual C++ itself.
- If an ordinary session works but shared cockpit fails, both pilots should install the same aircraft release and use the same panel and gauge set.
- If only one host causes the crash, have that host switch to a default aircraft before you join.
- If FSX displays a missing-aircraft message instead of crashing, use our aircraft definition and substitution checks.
- If the error starts before FSX joins the session, repair or reinstall the external multiplayer client and its documented x86 dependencies.
Does every player need the same Visual C++ package?
Each computer needs the runtimes required by its own FSX installation and add-ons; the host does not transmit a Visual C++ dependency to other players. Matching simulator updates and aircraft versions still matters, particularly for shared cockpit, but identical runtime inventories are not a multiplayer requirement.