Change FSX AI traffic density correctly and safely adjust schedules, parking, runway use and aircraft behaviour.
In FSX and FSX: Steam Edition, open Display settings, select the Traffic tab, then adjust Airline traffic density and General aviation traffic density. Those sliders control which scheduled AI flight plans are eligible to run; they do not alter routes, liveries, parking logic or flying characteristics, which require traffic, airport or aircraft configuration changes.
How do I change FSX AI traffic density?
Use the Traffic tab to control airline and general-aviation activity independently.
- Open Display settings. From the main screen, open Settings and the display customisation window. During a flight, press
Altif necessary and use Options, Settings, then Display. - Select the Traffic tab. FSX and FSX: Steam Edition use the same traffic controls, although the route to the window differs slightly depending on whether a flight is running.
- Set Airline traffic density. This controls flight plans compiled as airline traffic, including compatible add-on airline schedules.
- Set General aviation traffic density. This controls eligible GA flight plans separately.
- Apply the change. FSX may take a short time to add or remove nearby aircraft. Reloading the flight gives a cleaner comparison when testing the same airport and time.
Airport vehicles, road vehicles, ships and leisure boats have separate sliders. They add simulator activity and processing load, but they do not increase the number of AI aircraft.
The density values normally persist between sessions. If they reset whenever FSX starts, check that the active per-user FSX.cfg is writable and not marked read-only. The equivalent values are stored under [TrafficManager], but manual editing is rarely necessary.
What do the FSX traffic density percentages mean?
The percentage is an eligibility threshold, not a random sample of the available aircraft.
Each compiled flight plan has an activity percentage. A plan assigned 35% becomes eligible when the relevant slider is at 35% or higher; at 34%, it does not run. Setting the slider to 50% therefore does not simply display half of every airline or half the aircraft at each airport.
A mistake we see frequently is assuming every add-on scales smoothly. If a package assigns all its plans a 1% threshold, almost all of that package can appear with the slider at 1%, then disappear only at 0%. Conversely, raising the slider may produce sudden clusters when many plans share the same threshold.
Even at 100%, not every eligible aircraft is guaranteed to appear. The schedule time, available parking, aircraft references and FSX's nearby traffic-loading area still determine what is instantiated.
Can the traffic sliders change AI behaviour?
No—the Traffic sliders alter activity levels, not the AI engine's decision-making or the contents of its schedules.
| Change wanted | What controls it | Main caution |
|---|---|---|
| Routes, times and frequency | Compiled traffic BGL flight plans; use an FSX-compatible compiler or generator to build and compile custom FSX schedules | Do not edit a binary BGL as text, and avoid leaving old and replacement schedules active together. |
| Airline and gate parking | Airport parking types, codes and spot sizes, matched with atc_parking_codes and atc_parking_types in the aircraft variation | A coded gate still needs sufficient radius for the aircraft. |
| Taxi routes and runway availability | The airport facility BGL, combined with wind and ATC runway selection | Broken links, unsuitable hold-short nodes or closed runway settings can prevent normal movement. |
| Speed, climb and landing characteristics | The AI aircraft's configuration and air data | Editing a default flyable aircraft may also change how it behaves when flown by the user. |
Core behaviour such as ATC separation, pushback quirks, taxi decision-making and many go-around decisions is largely hard-coded. Airport and aircraft edits can improve the conditions under which AI operates, but there is no standard menu control for rewriting that logic.
The stock global schedule is normally held in Scenery\World\Scenery\trafficAircraft.bgl, while add-ons may place traffic BGLs in other active scenery folders. Our folder-by-folder traffic BGL location guide explains where to look. Copy an original file outside active scenery folders before replacing or recompiling it.
Why does changing AI traffic density have little or no effect?
If the slider changes nothing, FSX usually lacks an eligible, usable flight plan rather than ignoring the setting.
- No plans cross the new threshold: moving from 20% to 30% has no visible effect if the installed schedules use thresholds of 1% and 50%.
- Parking is unavailable: an airport may have too few spaces, spots that are too small, or parking codes and types that do not match the aircraft.
- An aircraft reference is missing: compiled schedules must refer to an installed aircraft title exactly. A missing or renamed model prevents that traffic from appearing.
- The stock BGL is disabled: replacing, renaming or removing
trafficAircraft.bgleliminates default schedules even when the sliders are high. - A legacy traffic file conflicts: an FS2004-format traffic BGL can suppress FSX-format traffic, sometimes across the simulator rather than at one airport.
- The flight has not repopulated: wait for nearby traffic to update or reload the flight after making a large density change.
For stubborn cases, use our diagnostic checklist for BGL conflicts, slider settings and missing aircraft references. The same checks apply to many traffic packages, not just World of AI installations.
Which FSX AI traffic density should I use?
There is no universal best density; use the lowest setting that provides the activity you want without unstable frame times, long runway queues or repeated go-arounds.
We recommend starting around 30% for airlines and 20% for GA, then raising one slider at a time in 10-point steps while testing the same busy airport, time and weather. Reverse those priorities if small-airfield flying matters more than airline traffic. At a congested hub, 100% can produce less convincing operations because FSX's airport and ATC logic struggles with the resulting queues.
AI aircraft consume CPU time, while airport and road vehicles add their own load. If traffic causes stutters, reduce road vehicles and airport vehicles first if they are less important to you, then lower airline or GA density. Our FSX performance-tuning steps for AI and vehicle traffic cover the wider settings that affect this balance.