Can't save aircraft.cfg in FSX on Windows 10 or 11? Fix UAC permissions, .txt extensions, VirtualStore redirects and wrong-install edits safely.
FSX usually cannot save aircraft.cfg changes because Windows protects files under Program Files and the editor lacks administrator permission. Close FSX, back up the file, edit a copy outside the FSX folder, then copy it back and approve the UAC prompt. Do not confuse aircraft.cfg with the separate FSX.cfg file.
Why does Windows block aircraft.cfg changes?
On Windows 10 and 11, a text editor running normally cannot overwrite protected files inside Program Files, where FSX and FSX: Steam Edition are commonly installed. An administrator account does not bypass this automatically; the editor or replacement operation must receive elevated permission.
The active aircraft file is inside that aircraft's folder, not the main FSX configuration directory:
| FSX edition | Typical aircraft.cfg location | Common mistake |
|---|---|---|
| Boxed FSX | <FSX installation folder>\SimObjects\Airplanes\<aircraft folder>\aircraft.cfg | Editing a downloaded or backup copy instead of the installed aircraft |
| FSX: Steam Edition | <Steam library>\steamapps\common\FSX\SimObjects\Airplanes\<aircraft folder>\aircraft.cfg | Editing the boxed FSX installation when Steam Edition is being run |
Installation folders can be customised. Our walkthrough of FSX aircraft folder placement explains how to identify the correct location and avoid configuration files accidentally saved as text documents.
How do I save aircraft.cfg changes safely?
The safest method is to edit a working copy and then replace the protected original with Windows approval.
- Close FSX and any add-on manager. This prevents another program from reloading or restoring the file while it is being changed.
- Locate the active aircraft folder. Check that it belongs to the FSX edition you actually launch. The folder name may differ from the aircraft name shown in the selection menu.
- Create a backup outside the FSX directory. Copy the original
aircraft.cfgto Documents or another writable folder before making changes. - Check the file attribute. Open the original file's Properties. If the individual file has Read-only selected, clear it. A shaded Read-only box on the aircraft folder itself does not necessarily mean its contents are locked.
- Edit the working copy. Use a plain-text editor, preserve the section headings and brackets, and make only the intended change.
- Save the exact filename. Confirm that it remains
aircraft.cfg, notaircraft.cfg.txt. If the editor offers a file-type choice, select the option that permits all files. Enabling file-name extensions in File Explorer makes this error visible. - Copy the edited file back. Place it in the aircraft folder, choose to replace the existing file, and approve the User Account Control prompt.
- Restart FSX and reload the aircraft. A full restart is the reliable way to make FSX read the revised configuration.
Alternatively, open Notepad or another trusted editor with Run as administrator, then use its Open command to load the installed file. We generally favour the copy-edit-replace method because it does not leave a text editor running with elevated rights.
What if aircraft.cfg still gives an Access denied error?
A continuing Access denied message usually points to damaged folder permissions, security software or a file controlled by an add-on utility.
- Damaged FSX permissions: if even an approved replacement fails, review what ResetXDirectorySecurity.exe changes before using it on the correct FSX installation. Do not grant Everyone full control over the whole Program Files tree.
- Windows Security or antivirus blocking: check its protection history for a specific block against the editor. Allow the trusted application where appropriate rather than disabling protection permanently.
- Add-on configuration manager: some aircraft utilities regenerate configuration files. Make the setting through that utility when possible, or ensure it is closed before editing.
- Wrong user or inherited permissions: files copied from another Windows installation can retain unusual access rules. Back up the aircraft before repairing permissions or reinstalling it.
Why did FSX ignore a saved aircraft.cfg change?
If the save appeared successful but FSX did not change, the usual cause is the wrong file, a hidden extension or a redirected copy.
- Two FSX installations: boxed FSX and Steam Edition can coexist, each with its own aircraft folders. Check the edition being launched; our guidance on using add-ons with FSX: Steam Edition covers the installation differences.
- VirtualStore redirection: an older, non-elevated editor may place its saved copy under
%LOCALAPPDATA%\VirtualStore\, mirroring part of the protected installation path. Preserve any useful edits, then update the real file in the FSX aircraft folder. - Hidden
.txtextension: Windows may displayaircraft.cfg.txtas though it were the correct file when extensions are hidden. FSX will not use it as the aircraft configuration. - Invalid configuration: a damaged section heading, missing bracket or unsuitable value can make the edit ineffective and may remove an aircraft variation from the menu. Restore the backup if that happens.
aircraft.cfg controls one installed aircraft. The separate FSX.cfg stores simulator-wide settings in the Windows user profile; see how to find the real FSX.cfg file if that is the configuration you intended to change.