What [fltsim.x] entries control in FSX aircraft.cfg, how folder suffixes work, and how to fix missing liveries, duplicate titles and AIR-file errors.
In FSX and FSX: Steam Edition, each numbered [fltsim.x] block registers one aircraft variation, usually a livery. It links that variation to an AIR file, model, panel, sounds and texture folder, then supplies its aircraft-menu and ATC labels. The block selects components; it does not itself contain flight-performance data.
What does the x mean in [fltsim.x]?
The x is a placeholder for a number, not a character entered literally. The first variation is normally [fltsim.0], followed by [fltsim.1], [fltsim.2] and so forth.
That number distinguishes configuration blocks; it does not have to match a texture-folder suffix, registration or livery name. Keep the sequence consecutive because FSX may stop enumerating variations after a gap. Duplicate section numbers and a header left as [fltsim.x] are common reasons for later entries being ignored.
Which aircraft.cfg fields does [fltsim.x] control?
A [fltsim.x] block chiefly identifies the variation, selects its component folders and controls how it is presented in the aircraft menu and to FSX ATC.
| Field | Purpose |
|---|---|
title= | The variation’s internal identity. It should be unique across the installed aircraft because saved flights, traffic and other add-ons can refer to it. |
sim= | Selects the aircraft’s .air file by base name. For example, sim=MyAircraft refers to MyAircraft.air. |
model= | Selects a model folder. A blank value normally uses model; model=winglet uses model.winglet. |
panel= | Selects the panel folder or a panel alias. Blank normally means panel, while panel=wide points to panel.wide. |
sound= | Selects the sound folder or sound alias using the same suffix convention. |
texture= | Selects the texture folder. texture=Blue points to texture.Blue; a blank value points to texture. |
ui_manufacturer=, ui_type=, ui_variation= | Provide the manufacturer, aircraft type and variation labels shown in the aircraft-selection menu. |
ui_typerole=, ui_createdby= | Supply further menu classification and publisher information used by FSX filters. |
atc_id=, atc_airline=, atc_flight_number= | Set the registration, recognised airline callsign and flight number used by FSX ATC where applicable. |
atc_parking_types=, atc_parking_codes= | Help AI traffic choose suitable parking positions when those values are used by the aircraft and scenery. |
kb_checklists=, kb_reference=, description= | Associate checklist, reference and descriptive information with the variation. |
title= and ui_variation= are not interchangeable. The title is an internal key, while the UI variation is the human-readable livery name. Two entries may accidentally display the same variation label, but their title= values must still be different.
How do the model, panel, sound and texture suffixes work?
The value after the equals sign is only the part following the period in the folder name. If the folder is texture.Red, enter texture=Red, not texture=texture.Red and not a full Windows path.
texture=Blueselectstexture.Blue.model=cargoselectsmodel.cargo.panel=glassselectspanel.glass.sound=aliasselectssound.alias.sim=MyAircraftselectsMyAircraft.air;sim=is not a folder-suffix field.
A panel or sound folder may itself contain an alias to another installed aircraft. The [fltsim.x] entry still selects the local suffix; the alias configuration inside that folder handles the shared files.
The chosen model and repaint must also be compatible. A texture set made for one model variant may omit mappings or files required by another, even when the texture-folder name is correct.
How do I add a new [fltsim.x] entry safely?
The safest method is to copy the closest compatible entry in the same aircraft folder and alter only the values needed for the new variation.
- Close FSX and back up aircraft.cfg. If there are several installations or Windows refuses to save the file, use our guide to finding and safely editing the active aircraft.cfg.
- Copy a matching variation. For a repaint, choose an entry that already uses the required
sim=,model=,panel=andsound=values. - Assign the next consecutive number. If the final block is
[fltsim.4], make the new one[fltsim.5]. - Create a unique title. Do not reuse the original
title=, even if you changeui_variation=. - Match the texture folder. A folder named
texture.BArequirestexture=BA. - Change the menu and ATC labels. Set the variation, registration and callsign details supplied with the repaint. Leave component references unchanged unless its instructions require a different variant.
- Save the original filename and restart FSX. Confirm that the editor did not create
aircraft.cfg.txtor save a copy elsewhere.
The surrounding folder-copying process is covered in our practical example of adding a livery to an FSX add-on aircraft.
Why does a new fltsim entry not appear in FSX?
A completely absent variation usually indicates a broken section header, duplicate identity, invalid file reference, menu filter or edit made in the wrong installation.
- Bad numbering: look for a duplicate number, a gap or a header still written as
[fltsim.x]. - Duplicate title: make the complete
title=value unique, not just the visible variation name. - Invalid AIR-file reference: ensure
sim=exactly matches the required.airfilename without the extension. - Malformed section: both square brackets must be present, and the entry must not have been pasted inside another configuration section.
- Aircraft-selection filters: enable Show all variations and clear manufacturer, type or publisher filters.
- Wrong aircraft.cfg: boxed FSX and FSX: Steam Edition can coexist, and similarly named aircraft folders are easily confused.
- Unloaded or unsaved edit: restart FSX, then reopen the file and verify that the new block is still present.
Why does the variation appear with missing or black textures?
A listed aircraft with white, black, transparent or incomplete surfaces has passed the basic [fltsim.x] registration stage. Check the texture= suffix, repaint files and compatibility with the selected model= variant.
Many aircraft also use a texture.cfg file inside the livery folder to obtain shared cockpit, reflection and detail textures through fallback paths. A missing or incorrect fallback can leave only part of the aircraft untextured.
Why does a saved flight report “Aircraft not defined”?
FSX stores the aircraft variation’s title= value in saved flights. Renaming or removing that title can therefore produce an “Aircraft not defined” message even though the aircraft files remain installed; our steps for repairing that saved-flight aircraft reference explain the available fixes.
Does [fltsim.x] change the aircraft’s flight model?
No—changing a livery’s title=, texture= or UI labels does not alter thrust, drag, weight or handling. Those characteristics come primarily from the AIR file and performance-related sections elsewhere in aircraft.cfg.
The sim= field can affect performance indirectly because it selects the AIR file. Most repaint entries should retain the aircraft’s existing sim= value; change it only when the aircraft developer supplies a different AIR file for that variant.
Are “fltsim” and “fltsim.to” the same as [fltsim.x]?
No: in FSX, [fltsim.x] is an aircraft.cfg section header. The search terms “fltsim” and “fltsim.to” do not identify another required FSX file, folder or configuration command.
Microsoft Flight Simulator 2020 and 2024 can also use related [FLTSIM.n] configuration entries, but their aircraft and liveries live within a different package system. Do not install an FSX repaint by copying its configuration block into a newer-simulator package; use files and instructions made for that simulator, such as the packages in our Microsoft Flight Simulator add-on library.