Fixing 'A Fatal Error Occured' in FSX

For many people, using Microsoft Flight Simulator X can be a seamless experience – everything goes fine, it runs perfectly smoothly, and its performance is spectacular. For others, though, the story is not quite the same; numerous errors, incompatibilities, bugs and problems have caused the performance to suffer greatly for many, and even the outright playability of FSX in total for others.

These problems, as you might imagine, are hugely frustrating and if you have come up against something similar in the past you might be able to find a solution here – we want to look at the “Fatal error occurred” problem.

This is a common issue that quite a lot of users have been talking about on various forums and locations across the web about; it’s an issue that outright halts the simulator and closes it back to the desktop in the vast majority of occasions.

This leaves you with all of your progress in that flight gone, having to start again from scratch – never ideal. However, this can be countered by looking into the solutions that can be available with the fatal error that has occurred in the first place. The reasons can be varied, however.

The Fatal Error message box in FSX

What is the Fatal Error That Is Occurring?

Given the rather radical name provided to this error, as you can imagine the problem(s) that occur are typically quite serious issues and need to be resolved with a relative level of care if you hope to find a suitable way out of the problem. The error itself – which can be caused by so many different things – stops the game dead as described above, and your only solution to get back into FSX is to start it back up from scratch.

The problem with the error is that you need to do a fair bit of detective work to get the solution back – it takes a lot of looking around, trial and error, and sometimes even just a bit of luck. While some of the errors can be caused by relatively obvious and easy to solve problems, the majority will find that their problem is rather insignificantly placed somewhere within the complex labyrinth that is the code for FSX. Your chances of being able to decipher the problem are, at times, fairly minimal.

Like many simulators and games out there, the overall ability to find a solution and make it work is quite hard to come across – you will typically find that it’s not even possible in most circumstances. Given the huge coded constructs that make up software these days, it’s not really surprising that some crossed wires in there exist somewhere – the key, then, is finding the easiest way to solve your own problem.

One thing that you can rule out, for a start, is that the cause could be something along the lines of a multiplayer server that you are using. This simply won’t the cause, as these fatal errors are within the files that you have at the moment – nothing that you will be using when going into multiplayer will be affected in the slightest bit, so if you have been wondering about that you will most likely find that it isn’t going to the case.

Out of all of our research, testing and reading we have yet to come across a solution that was brought about by not playing in the multiplayer section – therefore, the problems are going to be a little closer to home. This makes finding the problem a little easier, we guess!

Possible Causes of the Error

One of the big causes that many have reported to have helped – and we noticed ourselves on one occasion – was that the possible causes of the error can be hardware based. For a start, it can be brought about by your machine being too strained when using the software – it simply cannot cope. Look around at the minimum specifications for the simulator and see if your own PC compares to it. if you go to My Computer and right-click on it, and go to Properties, you should be able to find your own system specifications buried away somewhere in there.

This will help you work out if you are using a strong enough machine to actually use the software – another problem that can come up is going to be from the build-up in your machine. Over time your power supply, fan, graphics card etc. will get quite dusty and this will eventually impact on performance. not only will things be working harder to be heard and risk overdoing it, they also heat up the machine too much and this can cause things to go awry. Therefore, you should look into cleaning out the interior of your PC – but make sure you do it with the right tools instead of taking a risk and blowing something. It’s not a regular cause but for those who are suffering and cannot find a solution, this is well worth trying out.

A common problem that some face when having fatal errors at startup is by changing the Compatibility mode of their program. If you are using the Steam Edition then this isn’t likely to be a problem but older copies of FSX running on newer Windows OSs might be struggling. We recommend right-clicking on the shortcut for FSX, and changing the compatibility mode there.

Change it to Windows XP, and see if that helps at all – again, it’s not always going to fix the problem but for those suffering it at start-up it can be worth a try. User mrzippy offers a perfect explanation for how to get the ‘Faulting Module’ and this will easily give you the information that you need in a rather cryptic format. If you have no luck in finding a solution, it’s worth posting this faulting code on the support forums for FSX. Someone might have experienced the same code and have a solution for you – we just want to try and explore every potential avenue.

How Can It Be Solved?

There’s plenty for you to look at in terms of solutions – the issue comes down to the problem itself being so varied and vague. However, there is one useful solution out there that we regularly came across, and have tested out to relative success ourselves. We will note that it hasn’t sorted every “fatal error occurred” problem on each machine that we have tried it with, but it’s worked for a huge selection of people all across the web.

It seems to particularly make a difference those on modern machine and operating systems who are struggling to even get the thing to load up before the error occurs. If anyone is in this position and is struggling to find a solution, we really recommend trying this.

The first suggestion that we recommend is this – try out this tool. It’s a software tool created by Jesus Altuve, and it works to tweak and suggest your settings and what should be changed. It takes a total analysis of how you run FSX at the moment, compares it with what it should be doing, and provides an optimal list of changes for you to implement. Just making these changes alone has proven to be a very useful solution. Just make sure that you make a copy of the fsx.cfg file that you have at the moment.

This will make a big difference in helping you find a genuine solution later on if this does not work – it won’t really help using a modified fsx.cfg file later on down the track. Again, this solution will not work for everyone but we have seen it have a big change for many other users. The process itself is very well explained on the website, so you can easily work out what it is that you need to do just by having a quick read through that and getting a basic understanding for what you need to do when taking this forward.

Another welcome suggestion that we have seen success with is to use a DLL change that can help with the problem – many find that their problem tends to relate back to two specific DLL files that are causing carnage with their setup. The first thing that you should do, then, is check out a simple change. First off, make the change with the compatibility as we suggested earlier on in the guide, and then download the UIautomationcore.dll file from the excellent FSXEU site.

This file will be put in your FSX folder, and nowhere else – don’t place it any kind of system folders as it can cause untold damage elsewhere on your PC!

Instead, put it in the FSX folder and see if it helps. This is a suggestion many have got a lot of aid from but we do stress that this is just a suggestion – there’s no guarantee it will work, and we take no responsibility if you do decide to give this a try. The DLL file is called UIAutomationCore.dll and is known to cause a lot of problems throughout FSX support forums. It has solved the issue for many people, and might be worth trying out yourself to see if it can help you out at all.

The problem is very diverse, and these two solutions have been the most widespread. However, the problems can be created by anything from an add-on to a problem with the way the sound is being used; the issues are so minimal, too, it’s impossible to pinpoint.

Helpful Suggestions

The first other suggestion we can offer that has helped other people in the past is that you turn off all add-ons – particularly UI add-ons and aircraft add-ons. Take them off and if you find that the problems are being stopped then it might be a compatibility issue with that specific add-on.

These problems are fairly common and you need to watch out for them. I might take a lot of time to try this out if you use various add-ons as it can be caused by something not even being used by you at that point in time, so a trial and error system is really going to be your best bet here in getting this to work for you and to see if you can perhaps find a solution along the way.

The next thing that you need to think about is if you are using the right kind of mods with your own version – compatibility errors can be hard to spot at first but they are at the root of the causes for many people when it comes to problems with FSX and the dreaded fated error message that can pop up.

Lastly, the other thing we recommend that you try is to go through a full uninstall and reinstall. Make sure you keep all your mods and addons somewhere else and try a fresh installation. Delete everything and make sure it’s fully uninstalled, with nothing left behind in the old folders, and then try a clear start with nothing else added in. try that for a few days and see how it works – then start slowly adding in add-ons until you find the one that is causing the problems.

Sometimes, the issue is created by mods, other times its purely be a bad installation that never quite worked out the way it was supposed to!


As you can see, the fatal error is so hard to notice that it can be nearly impossible to get where you need to be in terms of finding a solution and making it work for you. It will take a lot of looking around and a lot of searching if none of the above works, as it most likely means that you are dealing with a very obscure problem – in this case, troubleshooting on forums or with Microsoft support may be your best bet.

Download iconDon't forget... We have a huge selection (over 24,000 files) of free mods and add-ons for MSFS, FSX, P3D & X-Plane in the file library. Files include aircraft, scenery, and utilities All are free-to-download and use - you don't even need to register. Browse on down to the file library here.

Ian Stephens

Ian Stephens

Ian Stephens is a flight simulation industry expert with over 20 years of experience and also has a keen interest in aviation and technology. Ian spends a lot of his time experimenting with various simulator packages but has a love for Microsoft Flight Simulator X because of the huge selection of add-ons available. However, Ian also has copies of Prepar3D and X-Plane installed.

Ian has been writing for Fly Away Simulation for over 9 years. Should you wish, you can contact Ian via email at


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The content of the comments below are entirely the opinions of the individual posting the comment and do not always reflect the views of Fly Away Simulation. We moderate all comments manually before they are approved.

MrHenkkaFri, 13 Nov 2015 14:13:13 GMT

I have this problem but this is helpful.

Sorry for my English, I'm from Finland.

MrToulouseSun, 22 Nov 2015 22:53:17 GMT

I was having that 'Fatal Error' problem too.

Downloaded the .dll mentioned but also rebuilt the FSX.cfg file from scratch - Has run fine since!

Oscar C SalinasSun, 19 Feb 2017 02:34:18 GMT

I have W10. Last july 2016 i installed FSX steam edition. Six months later I cleaned my PC and took out the game. Then I tried to reinstall it and there was an error that would not complete the installation. Support from Steam and Valve took me nowhere. That means that I lost the game and my money. They refuse to reinstall the game for me.

Jimmy CarterMon, 10 Dec 2018 07:07:09 GMT

Yes true problem because of too old FSX same FSX SE are too oldest now. Need next to new version near the future. Windows 10 as DirectX 12 not help not match with FSX SE. I had seen many FSX Crash Report notepad too many in FSX folder put as save into the folder. A Very Awful FSX SE crash! FSX SE is too old. We must to be wait for next to new version. Alike that one P3D and Xp11 still problem. Depends their graphics card and pci card can control that old FSX/FSX SE not true successful.

James LehmanMon, 10 Feb 2020 18:35:05 GMT

First of all, I want to thank you for giving me a chance to discuss what may be a simple solution to a problem with my FS2004 program. I have a WIN10Pro O/S using an HP Desktop Computer.

The problem is this: the program will download completely, however even before I can hit the program Icon everything disappears...I have no idea where it went. It's as if the download wizard had discovered the yellow brick road and ran off with it to auntie Ems's house.

I also, unfortunately, have three (3) FSX programs none of which will completely download. They get to about 95% complete and I get a notice it will not complete. (We are not going to deal with that at this time). I also have an FS2002Pro Program that works just fine and I am going to download some of your excellent aircraft that is if I can figure out to do it. Stay tuned for further bulletins. Jim.

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