Fix square halos around FSX aircraft lights by restoring halo and effect textures, checking DX10 Preview, and isolating add-on conflicts.
Square halos around aircraft exterior lights in Microsoft Flight Simulator X (FSX), including Steam Edition, usually mean a shared light texture has lost its alpha transparency or an add-on has replaced it. Restore the stock halo.bmp and affected effect textures, test a default aircraft, then check DX10 Preview and the shader cache.
Why do FSX lights turn into square boxes?
The square is the rectangular source bitmap becoming visible because FSX is not applying its transparency correctly. Light textures contain both the visible glow and an alpha channel that makes the area surrounding it transparent; a damaged, incorrectly saved or incompatible texture exposes the whole image.
The scope of the fault identifies where to look:
| What is affected? | Likely cause | Best first action |
|---|---|---|
| Every aircraft and some airport lights | Shared halo.bmp replaced or damaged | Restore [FSX]\Texture\halo.bmp |
| Navigation, beacon or strobe lights on every aircraft | Shared effect texture or effect file | Restore the relevant files under [FSX]\Effects |
| Only one add-on aircraft | Aircraft-specific effect, texture or installation conflict | Reinstall that aircraft's lighting files |
| Only DX10 Preview | Legacy effect or shader incompatibility | Test in DX9 mode and rebuild the shader cache |
How do I restore the FSX light textures?
Restore the original shared textures first when the fault appears on every aircraft. Do not edit halo.bmp in an ordinary image editor: saving it without the correct alpha channel or texture format can recreate the square immediately.
- Confirm the scope. Load a default aircraft at night in an external view. Operate the navigation, beacon, strobe, taxi and landing lights separately, and check whether airport lights also have boxes.
- Close FSX and make backups. Back up
[FSX]\Texture\halo.bmp, the[FSX]\Effectsfolder and itstexturesubfolder before replacing anything. This preserves files installed by lighting and aircraft add-ons. - Restore
halo.bmp. Use a known-clean copy from the same FSX installation, Steam's Verify integrity command, or the boxed edition installer's Repair option. Verification and repair can overwrite modified stock files, so retain the backup. - Restore affected effect files. If navigation, beacon or strobe lights remain square, restore the stock effect definitions and their referenced textures under
[FSX]\Effects. Replace only the affected files rather than copying an entire Effects folder over the installation. - Test before reinstalling add-ons. Start FSX with a default aircraft. If the lights are clean, reintroduce lighting or aircraft modifications one package at a time until the culprit is identified.
When the fault is limited to landing or taxi illumination, our replacement landing-light effects package and notes on the shared halo texture can help diagnose the files involved. Back up every file the package replaces.
Will Steam verification remove FSX add-ons?
Steam verification normally restores missing or changed stock files without deleting unrelated extra files, but it can replace modified default textures and effects. Back up lighting, shader and effect modifications first, then reinstall only the compatible changes you still need.
What if only one aircraft has square lights?
A one-aircraft fault points to that aircraft's custom effect or texture rather than FSX's global halo. Reinstall the aircraft's effects from its original package and check whether the installer placed files in both the aircraft folder and the global Effects folder.
The aircraft's aircraft.cfg file contains a [lights] section whose entries name the effects used by each light. Do not alter the light types or position coordinates merely to remove a square; identify the named effect and restore its texture instead. A common mistake we see is copying another aircraft's complete [lights] section, which can leave lights floating in the wrong positions.
What if the squares appear only in DX10 Preview?
A fault confined to DX10 Preview is usually an effect or shader compatibility problem, not a damaged aircraft model. Turn off DX10 Preview in FSX's graphics settings, restart the simulator and repeat the default-aircraft test.
If DX9 works correctly, use DX9 or replace the incompatible custom effect with one intended for DX10 Preview. You can also close FSX and clear the generated Shaders or Shaders10 cache under FSX's local application-data folder; FSX rebuilds it at the next launch. Do not delete the installation's ShadersHLSL folder.
If the boxes appear only with Light bloom enabled, switch bloom off as a diagnostic and rebuild the shader cache. Bloom can expose an effect or driver-side transparency problem, but disabling it will not repair a genuinely damaged alpha texture.
Why are smoke and aircraft lights both square?
Squares on smoke, contrails and lights indicate a wider Effects texture problem. An add-on may have overwritten several shared textures, or the alpha information may have been lost during manual editing.
Restore the affected files in [FSX]\Effects\texture rather than concentrating only on halo.bmp. Our targeted black-smoke texture replacement and installation notes are useful when smoke particles are boxed as well, although that texture does not itself repair an aircraft light halo.