How do I fix the FSX out of memory error?
FSX’s ‘Your computer has run out of available memory’ error usually means its 32-bit virtual address space is exhausted, not that Windows has no RAM. Use a fully patched FSX build on 64-bit Windows, add HIGHMEMFIX=1, reduce memory-heavy scenery, aircraft and AI traffic, then isolate any leaking add-on.
Why does FSX report low memory when RAM is free?
Microsoft Flight Simulator X boxed and FSX: Steam Edition are 32-bit applications, so each FSX process has a limited virtual address space. A patched, large-address-aware version running under 64-bit Windows can use up to about 4 GB, but fragmentation or a failed allocation may trigger the error before that figure is reached.
This limit includes the simulator itself, aircraft models, virtual cockpits, gauges, terrain, airport scenery, textures, weather and AI traffic. Installing 16 or 32 GB of system RAM does not turn FSX into a 64-bit application, and the Windows page file cannot enlarge its address space.
Fix the FSX out-of-memory error step by step
The safest fix is to establish a clean baseline, then restore add-ons one at a time until the memory-heavy component reveals itself.
- Update the simulator: for boxed FSX, install Service Pack 2 or Acceleration. FSX: Steam Edition already uses the later code base and should be kept intact through Steam. An unpatched boxed installation has a more restrictive memory ceiling.
- Back up and edit the active configuration: close FSX and locate
fsx.cfgunder%APPDATA%\Microsoft\FSXor%APPDATA%\Microsoft\FSX-SE. Steam installations may use either folder name depending on their installation history. Under the existing[GRAPHICS]section, addHIGHMEMFIX=1; do not create a second[GRAPHICS]section. - Run a clean test flight: choose a default aircraft, clear weather and an area without third-party scenery. Set airline and general aviation traffic to zero temporarily. Restart FSX between tests because returning to the menu does not necessarily unload every gauge or module.
- Restore components individually: test the add-on aircraft first, followed by departure scenery, destination scenery, AI traffic and detailed weather. Changing one variable at a time is slower than enabling everything together, but it identifies the actual cause.
- Reset a damaged configuration: if the default test still fails, close FSX and rename
fsx.cfgtofsx.cfg.old. FSX will create a fresh file on its next launch. Reapply only essential settings andHIGHMEMFIX=1. - Leave the Windows page file enabled: use the Windows-managed setting unless there is a specific reason not to. This prevents system-wide commit failures, although it cannot remove FSX’s 32-bit limit.
HIGHMEMFIX=1 corrects certain high-memory graphics allocations, but it does not raise the application’s address-space ceiling or repair a leaking add-on. Our FSX.cfg performance and graphics-memory guidance covers this setting alongside other safe configuration adjustments.
Which settings save the most FSX memory?
Complex airport scenery, high-resolution aircraft textures and detailed AI models usually produce the largest practical reductions.
| Memory load | Best first change | Typical clue |
|---|---|---|
| Airport and regional scenery | Disable unused, duplicate or overlapping scenery layers | The error appears while approaching the same airport or region |
| Aircraft and virtual cockpit | Use a lower-resolution texture set or a less complex aircraft | The problem occurs only with one aircraft or livery |
| AI traffic | Reduce airline and general aviation traffic sliders | Failures cluster around busy hubs |
| Autogen and scenery complexity | Lower each setting by one step | Dense cities fail while rural flights remain stable |
| Weather | Reduce cloud draw distance and detailed cloud coverage | The error follows a weather update or dense cloud layer |
If an add-on supplies 2048- or 4096-pixel textures, setting TEXTURE_MAX_LOAD=1024 in fsx.cfg can reduce pressure substantially. Back up the file first because changing FSX display options may rewrite that value. Lowering screen resolution alone is rarely the best first fix.
How do I identify a leaking add-on?
A repeatable failure at one geographical location usually points to airport or regional scenery; a failure after a similar amount of flying time points more strongly to an aircraft gauge, module, weather engine or traffic component retaining memory.
Run the same route with a default aircraft and default scenery, then introduce one add-on for each repeat. Do not judge an aircraft by switching away from it during the same session, as some gauges and modules can remain resident until FSX closes.
Older installers may also place files in the boxed FSX location when Steam Edition is installed. Check our explanation of how add-ons behave in FSX: Steam Edition before copying duplicate modules or scenery into both installations.
Will more RAM, a page file or a 4 GB patch help?
More physical RAM and a managed page file can improve overall system headroom, but only 64-bit Windows and a properly patched FSX executable allow the simulator to use its maximum 32-bit address space.
| Change | Does it help? | Limitation |
|---|---|---|
| 64-bit Windows | Yes | Allows a large-address-aware FSX build more address space than 32-bit Windows |
| Additional physical RAM | Sometimes | Helps Windows and other applications, but does not remove FSX’s process limit |
| Windows-managed page file | Yes, for system stability | Does not expand FSX’s virtual address range |
| Third-party 4 GB patch | Normally unnecessary | FSX SP2, Acceleration and Steam Edition are normally already large-address aware |
Do not apply an unofficial executable patch blindly to an updated FSX installation; use the official service packs for boxed FSX instead. Compatibility mode and running as administrator can solve other legacy problems, but neither is an out-of-memory fix.
If a clean default flight still fails after rebuilding fsx.cfg, repair the boxed installation or verify the Steam files, remembering that verification can restore modified default files. If the message changes to a generic crash rather than the specific memory warning, follow our broader FSX fatal-error troubleshooting steps.