How do I replace AI aircraft models in FS2004?

To replace an AI aircraft model in FS2004, install an FS9-compatible replacement aircraft, copy the exact title= value from its aircraft.cfg, remap the relevant aircraft entry in the traffic file’s source list, and recompile the traffic BGL. Back up both aircraft folders and BGL files first.

How FS2004 identifies an AI aircraft

FS2004 traffic does not select an aircraft by its folder name or MDL filename; it uses the title= value from a specific [fltsim.x] entry. That title is also stored against an AC# entry in the traffic BGL.

This distinction matters. Renaming an aircraft folder will not redirect existing traffic, while changing or remapping the title will. Each installed livery should have a unique title.

Replace an FS2004 AI aircraft step by step

The safest method is to install the replacement as a complete aircraft package and then point the traffic plan at its title.

1. Back up the existing files. Copy the old AI aircraft folder and its traffic BGL somewhere outside every active FS2004 scenery folder. Add-on traffic BGLs may be in Scenery\World\scenery or another enabled scenery area.
2. Install the replacement aircraft. Put its main folder directly under the FS2004 Aircraft folder. Avoid an extra nested directory: Aircraft\Replacement\aircraft.cfg is valid, while Aircraft\Replacement\Replacement\aircraft.cfg usually is not.
3. Check the selected livery. Open aircraft.cfg, find the intended [fltsim.x] section and copy its complete title= value. Confirm that its model= and texture= entries point to folders that actually exist.
4. Obtain the traffic source files. Use the original source text files if you retained them. Otherwise, decompile the active BGL with the FS2004 Traffic Tools decompiler and compiler.
5. Change the aircraft mapping. In the aircraft source list, replace the old quoted title with the replacement title. For example, change AC#23,450,"Old AI title" to AC#23,450,"New AI title". Keep the same AC# number so the associated flight plans continue to work.
6. Recompile the traffic BGL. Compile the complete aircraft, airport and flight-plan source set. Activate the revised BGL only after it compiles successfully, and remove the original from the active scenery folder to prevent duplicate schedules.
7. Restart and test FS2004. Load an airport, day and time used by the affected flight plan. Set the AI traffic percentage high enough to include that plan, then check both parked and arriving traffic.

Changing one AC# mapping replaces every flight that references that number. To change only one operator or livery, remap only its corresponding aircraft entry. If you also need to create or install schedules, follow our complete FS2004 AI traffic installation workflow rather than duplicating the process here.

Should I edit aircraft.cfg or the traffic BGL?

Edit the traffic mapping for an ordinary aircraft replacement; alter model files or configuration entries only when the replacement was designed for that exact base package.

A model-only update can be safe when its instructions identify the required base aircraft and files. This example of an AI model update that preserves existing configuration entries illustrates that specialised case. Do not copy an unrelated MDL over the old one merely because the aircraft types look similar.

Can a flyable aircraft replace a dedicated AI model?

Yes, an FS9-compatible flyable aircraft can be assigned to AI traffic, but a dedicated AI model is normally the better choice. Flyable aircraft may include detailed virtual cockpits, panels and geometry that waste resources when many copies appear at a busy airport.

Never use an FSX-native model in FS2004. A valid folder and matching title cannot make an incompatible model format load in FS9.

Why does the replacement AI aircraft not appear?

A missing replacement usually means FS2004 cannot resolve its title or load the selected model and texture.

• Title mismatch: copy the entire title= value, including spaces and punctuation, and recompile the correct BGL.
• Duplicate title: move the old aircraft folder outside the FS2004 Aircraft directory or give its entry a different unique title.
• Nested installation: verify that aircraft.cfg sits directly inside the aircraft’s main folder.
• Broken configuration: check that sim=, model= and texture= reference the package’s actual files and subfolders.
• Wrong BGL active: confirm the revised traffic file is in an enabled scenery area and that an unchanged copy is not still supplying the same schedules.
• Traffic filtered out: check the flight plan’s traffic-percentage threshold, operating day, time and airport.
• Aircraft floating or sinking: this commonly follows grafting a new visual model onto the old configuration. Use the replacement’s complete folder and remap its title instead.