Fix the FSX “airplanes must have unique titles” error by finding duplicate aircraft.cfg entries, correcting them safely and protecting AI traffic.
FSX shows the “airplanes must have unique titles” error when two active [fltsim.x] entries use the same title= value. Close FSX, find both entries in the loaded SimObjects folders, then remove the accidental duplicate or give one title a genuinely unique value. Renumbering sections alone will not fix it.
Why FSX requires unique aircraft titles
FSX treats title= as a global internal identifier for an aircraft variation. Every title must be unique across every aircraft.cfg file FSX loads, not merely within one aircraft folder. This rule is the same in boxed FSX and FSX: Steam Edition.
The warning usually appears after one of these mistakes:
- A repaint's
[fltsim.x]block was copied without changing itstitle=line. - A complete aircraft folder was duplicated inside
SimObjects. - The same add-on was installed in two active
SimObjectPaths. - An installer added a livery that was already present.
Changing the aircraft folder name, ui_variation= or the [fltsim.x] number does not make the title unique. If the warning appeared after adding a repaint, compare its files with the correct aircraft and repaint installation structure before editing anything else.
How do I fix duplicate title entries?
Fix the warning by finding every matching title= line and keeping only one occurrence of that exact value.
- Close FSX and make backups. Copy each affected
aircraft.cfgsomewhere safe before editing it. - Record the reported title. If the error message identifies the duplicate, copy that text exactly. Otherwise, start with the aircraft or repaint installed immediately before the warning began.
- Search every loaded aircraft folder. The standard location ends in
SimObjects\Airplanes, although the full installation path differs between boxed and Steam editions. Add-ons may also be loaded from extra paths listed asSimObjectPaths.Nin the[Main]section of the active FSX configuration file. Search theaircraft.cfgfiles in all those locations for the duplicate title. - Choose the correct repair. If the same aircraft folder or livery was installed twice, remove the redundant copy. If two legitimate repaints share a title, change the newer repaint to a descriptive unique value such as
title=C172 Blue N123AB. Do not rely on capitalisation alone. - Remove complete duplicate blocks. If a repaint entry was pasted twice, delete the entire redundant
[fltsim.x]block rather than deleting only its title line. Renumber the remaining section headers consecutively from[fltsim.0]; repeated numbers and gaps can stop later repaints from loading, although they are not the cause of this particular warning. - Save and restart FSX. Preserve the file as plain text named
aircraft.cfg, notaircraft.cfg.txt. FSX may report duplicate titles one pair at a time, so a second warning can identify another separate conflict.
To disable a suspected duplicate temporarily, move its whole folder outside every configured SimObjects path. Merely renaming the folder while leaving it under SimObjects\Airplanes will not prevent FSX from scanning it.
Which aircraft.cfg value should I change?
Change title= only when both aircraft entries are legitimate; changes to display names or texture references will not resolve this error.
| Entry | Purpose | Does changing it fix the warning? |
|---|---|---|
title= | Global internal aircraft identifier | Yes, provided the new text is genuinely unique |
ui_variation= | Livery name shown in the aircraft-selection menu | No |
[fltsim.x] | Local configuration-block number | No, although each block in that file needs a sensible unique sequence |
texture= | Identifies the repaint's texture-folder suffix | No; an incorrect change can make the livery white or missing |
sim= | Identifies the aircraft model's flight-dynamics file | No; changing it can stop the aircraft loading |
Can changing the title break AI traffic?
Yes. AI traffic packages can refer to an aircraft by its exact title= value, and saved flights or missions may also expect that identifier. Changing the referenced title can make the intended aircraft disappear even though the duplicate-title warning is gone.
For an AI aircraft, preserve the title expected by the traffic package and remove or rename the accidental clone instead. If one entry is a normal user repaint and the other serves AI traffic, renaming the user repaint is usually the safer choice.
What if the aircraft disappears after the fix?
A missing aircraft after correcting its title usually indicates another aircraft.cfg problem, not a need to restore the duplicate value. Check that the remaining [fltsim.x] sections are consecutively numbered and that their sim=, model=, panel= and texture= references still point to valid files or folders.
If the add-on remains absent or incomplete, work through the configuration checks for invisible add-on aircraft. If it appears but has a plain white exterior, use our repaint and texture-folder checks rather than changing title= again.