You are two hours into a transatlantic flight in the PMDG 737. The FMC is programmed, the autopilot is on, everything is smooth. Then every instrument goes orange. Without warning. The PFDs, the FMC, the autopilot panel. Dead. The aircraft keeps flying, but the cockpit is a ghost ship. Congratulations: You have just had a WASM crash.
This is one of the most reported and most misunderstood problems in MSFS 2024. It is not a CTD. It is not a VRAM issue. The honest answer is that it is not fully fixed yet. Here is what you need to know.
What Is WASM?
WASM stands for WebAssembly. It is the technology that allows complex third-party aircraft like the PMDG 737, the PMDG 777, and the iniBuilds A320 family to run sophisticated avionics systems and flight models inside MSFS. Without WASM, aircraft developers could not build the kind of deep system simulations that serious simmers expect.
When a WASM module crashes, the aircraft systems shut down completely. The sim itself keeps running. The plane keeps flying on whatever state it was in at the moment of the crash. But you lose autopilot, FMC, displays. Effectively everything.
How to Recognise a WASM Crash
WASM crashes have a distinctive signature that separates them from other MSFS 2024 problems:
- Cockpit instruments go orange or red simultaneously
- The FMC screen freezes or goes blank
- Autopilot disengages and cannot be re-engaged
- All PMDG or iniBuilds system panels become unresponsive
- The aircraft continues to fly — the sim has not crashed
- No CTD, no error message — it just quietly dies
It can happen at any point in a flight, though most users report it occurring during FMC interaction, such as entering a flight plan, editing a STAR, requesting a route. It is intermittent, which makes it extremely difficult to reproduce and diagnose.
Why Does It Happen?
PMDG’s Robert Randazzo has been unusually transparent about this. According to PMDG, WASM crashes stem from instability in the way MSFS 2024 allocates dynamic memory for third-party add-on modules during normal operation. In plain language: the sim occasionally gives a WASM module corrupted or insufficient memory, and the module collapses as a result.
This is a platform-level problem. It is not caused by a bug in the PMDG 737 or the iniBuilds A320 specifically The cause is how MSFS manages memory for all WASM-based products. Multiple developers including PMDG, iniBuilds, and others have confirmed this independently and are sharing information with each other and with Asobo.
The consequence: no aircraft developer can fully fix this.
Which Aircraft Are Affected?
WASM crashes primarily affect complex payware aircraft that rely heavily on WASM for their systems simulation. The most commonly reported are:
- PMDG 737 family (600, 800, 900) for MSFS 2024
- PMDG 777 family
- iniBuilds A320 family (MSFS 2024 native version)
- Other complex airliners using WASM-based avionics
Default MSFS aircraft and simpler add-ons that do not rely on WASM are not affected. If you fly the default A320neo or a GA aircraft and have never seen this problem, that is why.
What Developers Are Doing About It
PMDG has pushed WASM stability updates across its 737 and 777 fleets. These updates do not eliminate the root cause. What they try is to reduce WASM crashes by minimising the memory operations that are most likely to trigger a crash. PMDG was also specific about one reproducible trigger: editing a flight path after sequencing the first fix on a STAR. That particular scenario has been patched.
PMDG has also added protections for situations where the 737 is running alongside other add-on products that appeared frequently in crash reports. The goal, in their words, is “measurable progress, not a complete solution.”
iniBuilds has similarly acknowledged the issue with its MSFS 2024 native Airbus products. Both developers continue to collect crash reports and patterns, and both are in contact with Asobo about a platform-level resolution.
What You Can Do Right Now
While the root fix remains outstanding, there are several things that reduce the frequency of WASM crashes considerably:
1. Keep Your Add-ons Updated
Both PMDG and iniBuilds have pushed stability patches specifically targeting WASM crashes. If you are not on the latest version of your aircraft, update now. This is the most impactful thing you can do.
2. Clear the WASM Cache
Corrupted WASM cache files in particular after sim updates or aircraft updates can increase crash frequency. Clearing the cache forces the sim to rebuild it clean.
Close MSFS 2024 completely, then navigate to the following path depending on your version:
Steam:
%APPDATA%\Microsoft Flight Simulator 2024\WASM\MSFS2024\
Microsoft Store:
%LOCALAPPDATA%\Packages\Microsoft.Limitless_8wekyb3d8bbwe\LocalState\WASM\MSFS2024\Open the folder for your specific aircraft and delete all .cache, .dll, .lib, and .obj files inside it. Do not delete the WORK folder. Restart the sim. The files will be rebuilt automatically on first load.
3. Keep Your Community Folder Lean
WASM crash frequency increases when multiple complex add-ons are loaded simultaneously. PMDG has noted that some crashes occur when the 737 runs alongside certain other add-on products. Run only what you actually need for a given flight. If you are doing a serious long-haul in the PMDG 737, consider removing unrelated complex add-ons from your Community folder for that session.
4. Avoid Aggressive FMC Editing at Cruise
Many users and developers have noted that WASM crashes are more likely to occur during intensive FMC interaction — particularly editing STARs or flight path waypoints late in the flight. This does not mean you cannot edit your routing, but being aware of this pattern lets you do it more carefully and save your state beforehand if the sim supports it.
5. If It Happens Mid-Flight: stay calm and carry on
There is no recovery from a WASM crash during a flight. Once the modules collapse, they cannot be restarted without ending the session. Your only option is to end the flight, restart the sim, and load a new session. Some users report that reloading from a saved state works if you have one close to the crash point.
The Honest Take
WASM crashes are a legitimate platform deficiency in MSFS 2024, not a user error and not a developer failure. The aircraft themselves are not broken. The environment they run in has a memory management problem that Microsoft has not yet resolved.
For most users on updated software with a lean Community folder, crashes are infrequent enough to be manageable. For others, they remain a source of frustration. The workarounds above reduce risk but do not eliminate it. MSFS2020 is an alternative after all: WASM crashes are a rarity there.
We will update this article when a platform-level fix is released. Until then, keep your aircraft updated, clear your WASM cache after every sim update, and fly lean.
→ Also read: MSFS 2024: Stutters, FPS Drops & Performance Issues – The Complete Fix Guide
