Change FSX traffic density, understand percentage thresholds, fix missing AI aircraft, edit behaviour and balance airline traffic against FPS.
In Microsoft Flight Simulator X (FSX) and FSX: Steam Edition, open Settings, choose Display, select the Traffic tab, and adjust Airline traffic density and General aviation traffic density. These percentages decide which scheduled AI flights may load; they do not change routes, parking, aircraft handling or the simulator’s hard-coded ATC behaviour.
How do I change FSX AI traffic density?
Use the Traffic tab to control scheduled airline and general-aviation aircraft independently.
- Open the display settings. Before loading a flight, select Settings and open the display customisation window. During a flight, press
Altif the menu is hidden, then use Options, Settings and Display. - Select the Traffic tab. FSX and FSX: Steam Edition provide the same main traffic controls, although the route to this window differs slightly in and out of a flight.
- Adjust Airline traffic density. This controls eligible flight plans categorised as airline traffic, including compatible add-on schedules.
- Adjust General aviation traffic density. This separately controls eligible GA flight plans.
- Apply the settings. Nearby aircraft may take time to appear or disappear. Reload the flight when comparing settings at the same airport and time.
Airport vehicles, road vehicles, ships and ferries, and leisure boats have separate sliders. They add activity and processing load but do not increase the number of AI aircraft.
The settings should persist between sessions. If they reset every time FSX starts, check that the active per-user FSX configuration file is writable and not marked read-only. The exact configuration filename can differ when boxed FSX and Steam Edition are installed side by side.
How do I turn FSX traffic off completely?
Set both aircraft density sliders to 0% to stop scheduled airline and GA traffic.
Set the vehicle and marine sliders to 0% as well if you want to remove those traffic types. Static aircraft built into airport scenery will remain, while traffic injected through an external SimConnect-based program may use that program’s own controls rather than the FSX sliders.
What do the FSX traffic density percentages mean?
The percentage is an activation threshold, not a random sample of all installed aircraft.
Each compiled flight plan has an activity percentage. A plan assigned 35% becomes eligible when its relevant slider is set to 35% or higher; at 34%, it does not run. A 50% setting therefore does not guarantee half the aircraft at every airport.
A mistake we see frequently is expecting every traffic package to scale smoothly. If all its plans have a 1% threshold, nearly the whole package can appear at 1%. If many plans share a 50% threshold, moving the slider from 49% to 50% can suddenly add a large group of flights.
Even at 100%, FSX will not necessarily display every eligible flight. The schedule time, available parking, installed aircraft references and simulator loading range still determine what appears around the user.
Can the traffic sliders change AI behaviour?
No; the Traffic sliders change activity levels, not routes, gate selection, aircraft performance or the underlying AI logic.
| Change wanted | What controls it | Common problem |
|---|---|---|
| Routes, times and frequency | Compiled traffic BGL flight plans; use an FSX-compatible tool to create and compile custom FSX traffic schedules | Old and replacement schedules left active together can create duplicate flights. |
| 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 correctly coded gate still needs a large enough parking radius. |
| Taxi routes and usable runways | The airport facility BGL, together with wind and ATC runway selection | Disconnected taxi links, unsuitable hold-short nodes or closed runway settings can stop normal movement. |
| Speed, climb and landing characteristics | The AI aircraft’s configuration and air data | Changing a flyable aircraft can also alter its behaviour when used by the player. |
| ATC separation and taxi decisions | Mostly hard-coded FSX logic | There is no standard setting that rewrites this behaviour. |
The stock traffic schedule is normally stored in Scenery\World\Scenery\trafficAircraft.bgl under the FSX installation. Add-ons may put traffic BGLs in other enabled scenery folders. Keep backups outside active scenery folders before replacing or recompiling a schedule.
Airport and aircraft edits can improve the conditions under which AI operates, but they cannot remove every FSX limitation. Dense hubs can still suffer long departure queues, late go-arounds, aircraft waiting indefinitely and abrupt disappearances.
Why does changing AI traffic density have little or no effect?
If moving the slider changes nothing, FSX usually has no eligible, usable flight plan to load at that place and time.
- No threshold was crossed: moving from 20% to 30% has no visible effect if the installed plans activate only at 1% and 50%.
- The schedule is not active then: test at the airport, day and time covered by the flight plan.
- Parking is unavailable: the airport may have too few spaces, undersized spots or parking codes that do not match the aircraft.
- The aircraft reference is missing: a traffic schedule must reference an installed aircraft title correctly. Renaming or removing the required variation prevents it from appearing.
- The traffic BGL is disabled: removing or renaming
trafficAircraft.bglremoves the default schedules. Some add-ons deliberately disable it to prevent fictional stock traffic, so do not restore it blindly. - A legacy traffic file conflicts: an active FS2004-format traffic BGL can suppress FSX-format traffic across the simulator, not only at the airport where that file was installed.
- An injector controls the traffic: externally injected aircraft may ignore the standard percentage thresholds.
- Traffic has not repopulated: allow FSX time to update nearby traffic or reload the flight after a large change.
For a package that remains empty, follow our checklist for slider settings, BGL conflicts, installation paths and missing AI aircraft. Although written around World of AI installations, the same faults affect many FSX traffic packages.
Why is AI traffic missing at only one airport?
When traffic works elsewhere, the affected airport usually lacks a suitable schedule, parking space or valid taxi network.
Check that flights are scheduled there at the selected time, then inspect parking quantity, radius, type and airline codes. An older duplicate airport facility can also take priority over the scenery you intended to use. Our airport-specific AI traffic checks cover these local failures without repeating the simulator-wide diagnosis.
Which FSX traffic density should I use?
Use the lowest density that gives the activity you want without unstable frame rates, excessive runway queues or repeated go-arounds.
A practical starting point is about 30% airline traffic and 20% GA traffic. Test the same busy airport, time and weather, then raise one slider at a time in 10-point steps. Reverse those priorities if you mainly fly from small airfields.
These percentages are only starting points because traffic packages assign activation thresholds differently. A package concentrated at 1% can be busier than another package at 50%, so settings cannot be compared reliably between installations.
At a congested hub, 100% traffic can look less convincing because FSX’s airport and ATC logic struggles with the queues. AI aircraft consume processor time, while detailed AI models and textures add rendering and memory demands. Road and airport vehicles create their own load, so reduce the traffic types you value least first.
If dense traffic causes pauses or poor frame pacing, use our wider FSX FPS and traffic-tuning steps to balance AI, vehicles, scenery and display settings.