Fix a WASM crash in Microsoft Flight Simulator by isolating faulty add-ons, testing Safe Mode, reinstalling packages and checking crash logs.
To fix a WASM crash in Microsoft Flight Simulator, start in Safe Mode, test a stock aircraft, then disable all Community and third-party Marketplace packages. Re-enable add-ons in batches until the crash returns, update or reinstall the culprit, and only troubleshoot Windows or the base simulator if a clean-content test still crashes.
What causes a WASM crash in MSFS?
Most WASM crashes in Microsoft Flight Simulator 2020 and 2024 come from an incompatible or damaged aircraft, avionics package or shared add-on dependency. WASM stands for WebAssembly; the simulator uses it to run aircraft systems and gauges within its own runtime.
Common causes include:
- An aircraft or instrument package built for an earlier simulator build.
- Old files left behind when a new add-on version was copied over the existing folder.
- Two versions of the same aircraft, livery or shared avionics library loading together.
- A missing dependency or a dependency intended for the wrong simulator generation.
- Corrupt package files or stale package-specific generated data.
A crash report mentioning FlightSimulator.exe does not by itself prove that WASM caused the crash. Blank instruments can also indicate a failed module without producing a full crash to desktop.
How do I isolate the faulty WASM add-on?
The decisive test is whether the same flight works with all third-party content disabled.
- Record the trigger. Note the aircraft, livery, airport and point at which the crash occurs. Retest with the same setup so that you change only one variable at a time.
- Use Safe Mode. After an abnormal shutdown, choose Safe Mode when Microsoft Flight Simulator offers it. Load a stock aircraft at a simple stock airport. If that works, a third-party package is the leading suspect.
- Empty the Community folder on PC. Close the simulator completely and move every package outside
Community. Do not place disabled packages in a subfolder inside it, because the simulator can still scan them. If symbolic links are involved, our guide to selectively disabling packages with MSFS Addons Linker explains a cleaner isolation method. - Test installed Marketplace content separately. If Safe Mode works but Normal Mode still crashes with an empty Community folder, uninstall or disable recently added third-party content through the simulator’s content-management or library screen. Do not manually alter encrypted packages in the Official folder. Console users should start with this step because they cannot perform a Community-folder test.
- Restore packages in batches. Enable half the add-ons, repeat the original flight, then keep dividing the failing group. This binary-search approach finds the culprit much faster than restoring packages individually from the start.
- Perform a clean package reinstall. Remove the identified package fully before installing a fresh copy. Do not extract a new version over an old one. Reinstall its required avionics libraries and confirm that the package explicitly supports MSFS 2020 or MSFS 2024 as applicable.
- Update both sides of the dependency. Install the completed simulator update and the aircraft or avionics update intended for it. A module compiled for an older interface may keep failing even though its files are intact.
What do the test results mean?
Each clean-content result narrows the failure to a different package group.
| Test result | Likely cause | Next action |
|---|---|---|
| Safe Mode works; Normal Mode crashes | Third-party Community or Marketplace content | Isolate both content groups |
| Empty Community folder fixes it | Community add-on or shared dependency | Restore packages in batches |
| Community is empty, Safe Mode works, Normal Mode crashes | Installed third-party Marketplace package | Disable or reinstall packages through the simulator |
| Only one aircraft crashes | Aircraft, livery, avionics or aircraft-specific data | Test the base aircraft without liveries, then reinstall it |
| Stock aircraft also crash in Safe Mode | Base package, driver, operating-system or hardware instability | Move beyond WASM-specific troubleshooting |
Should I clear the WASM cache or reinstall MSFS?
Usually, no: broad cache deletion and a complete simulator reinstall should not be the first fixes. The rolling cache stores streamed world data and does not repair an aircraft’s WASM module.
Start by reinstalling only the affected package. Delete package-specific generated data only when you can identify it confidently, because it may contain persistent aircraft state or configuration. Paths differ between simulator versions and PC store installations, so deleting every folder labelled as a cache can create a second problem.
Microsoft Flight Simulator supplies its own WASM runtime. Installing a browser WebAssembly component or an unrelated runtime package will not repair a faulty aircraft module.
What if MSFS still crashes with every add-on disabled?
A crash in Safe Mode with a stock aircraft is no longer strong evidence of an add-on WASM fault. Verify or reinstall the affected first-party aircraft package, complete pending simulator and operating-system updates, restore standard CPU and GPU clock settings, and test without overlays or background injectors.
If MSFS 2020 cannot reach the main menu, follow our recovery steps for startup failures and inaccessible content packages. Avoid repeatedly loading the same failing aircraft until the suspect package has been removed.
On PC, Reliability Monitor, Event Viewer and Windows Error Reporting may reveal an exception code or faulting component; our guide to locating the relevant Microsoft Flight Simulator crash records shows where to look. The records may name only the simulator rather than the individual WASM package, so use them alongside the clean-content tests rather than as sole proof.
If the logs point to a graphics driver, system library or general access violation and stock content also fails, continue with the broader ordered MSFS crash-isolation process. Disabling the simulator’s aircraft crash-detection setting will not help: that setting controls simulated flight damage, not crashes to desktop.