Set FSX to High priority in Windows Task Manager, fix Access denied, avoid Realtime, and understand why the setting resets.
Launch FSX or FSX: Steam Edition, open Windows Task Manager with Ctrl+Shift+Esc, select the Details tab, right-click fsx.exe, choose Set priority > High, and confirm Change priority. The setting lasts only for that FSX session; Windows normally resets it to Normal when you close and relaunch the simulator.
Set FSX to High priority step by step
The priority control is on Task Manager’s Details tab, not its main Processes view.
- Start FSX and wait until its menu or a flight has loaded.
- Open Task Manager by pressing
Ctrl+Shift+Esc. Select More details first if Windows displays the compact view. - Open the Details tab and find
fsx.exe. Both the boxed and Steam editions use this executable name. If necessary, find Microsoft Flight Simulator X under Processes, right-click it and select Go to details. - Set the priority by right-clicking
fsx.exeand selecting Set priority > High. - Confirm the change when Windows asks whether you want to change the priority.
A mistake we see constantly is changing the priority of Steam.exe, an add-on manager or Task Manager itself. Only fsx.exe controls the simulator’s priority.
Should FSX use High or Above normal priority?
Above normal is the safer first test; use High only when other active processes are competing for CPU time and the change produces a repeatable improvement.
| Priority | When to use it | Recommendation |
|---|---|---|
| Normal | FSX runs acceptably or the computer has little background activity | Best default |
| Above normal | You want to favour FSX without heavily deprioritising supporting software | Test this first |
| High | Background CPU load is affecting FSX and testing confirms a benefit | Use with care |
| Realtime | Never required for FSX | Avoid; it can interfere with audio, controls and Windows responsiveness |
Process priority changes scheduling preference; it does not give FSX more processor cores or remove its main-thread bottleneck. Our explanation of how FSX uses CPU cores and affinity covers that distinction.
High priority also cannot compensate for excessive traffic, dense autogen or demanding weather. If frame rate is the actual problem, use our broader FSX performance-tuning checklist before relying on Task Manager.
Why does Task Manager say Access is denied?
Access is denied usually means Task Manager lacks permission to alter the FSX process.
- Close Task Manager.
- Find Task Manager from the Windows Start menu.
- Right-click it and select Run as administrator.
- Return to Details, right-click
fsx.exeand set the priority again.
You do not normally need to configure FSX itself to run as administrator solely for this change. On a managed or standard Windows account, an administrator may need to approve it.
Can I make FSX High priority permanent?
Task Manager does not remember priority changes after fsx.exe exits, but a batch file can launch it at High priority each time.
After identifying the executable with our guidance on locating the FSX installation folder, replace both placeholder paths in this command and save it in a file ending in .bat:
start "" /high /d "C:\path\to\FSX" "C:\path\to\FSX\fsx.exe"
This does not permanently modify Windows; it applies High priority whenever that batch file launches FSX. If an aircraft or add-on requires its own launcher, use that launcher and change fsx.exe manually afterwards rather than bypassing it.
What if High priority does not improve FSX?
If High priority produces no repeatable improvement, return FSX to Normal because CPU priority was not the limiting factor.
Compare the same aircraft, airport, weather and view before and after changing it. For intermittent pauses rather than consistently low frame rates, follow our FSX stutter troubleshooting steps; frame caps, background programs and individual add-ons are more common causes than process priority.