Learn how a flight simulator chooses the active runway using wind, ATC, airport flow and runway data, plus why it may assign the wrong runway.
A flight simulator usually chooses the active runway by combining surface wind with airport runway data, closures, available approaches and traffic-flow rules. It generally favours a runway with a headwind and acceptable crosswind, but calm-weather defaults, AI limitations, scenery errors or an ATC assignment can produce a different result.
For general flight simulation—including Microsoft Flight Simulator, X-Plane, FSX and Prepar3D—the exact algorithm varies. An “active runway” may also mean an airport configuration: one runway for departures, another for arrivals, or several parallel runways operating together.
What determines the active runway?
The active runway is usually the result of several priorities rather than a wind-only calculation.
| Factor | How it affects runway selection |
|---|---|
| Surface wind | The simulator normally favours a runway pointing into the wind while checking crosswind and tailwind components. |
| Runway availability | Airport data can mark a runway closed, unavailable for take-off or landing, or restricted to a particular direction. |
| Runway suitability | Length, width, surface and available instrument approaches may influence the choice, although basic simulator ATC does not always assess aircraft performance accurately. |
| Visibility and approaches | Low visibility can favour a runway equipped with a suitable instrument approach rather than the runway most closely aligned with the wind. |
| Airport flow and traffic | Parallel-runway operations, arriving AI aircraft and established traffic can delay a runway change after the wind shifts. |
| ATC authority | Built-in ATC, an add-on controller or a human online controller can assign a runway that overrides the pilot’s prediction. |
Runway numbers indicate approximate magnetic direction with the final zero removed. Runway 27 therefore points roughly towards 270°. With wind reported from 260°, runway 27 offers a near-headwind while reciprocal runway 09 would have a substantial tailwind.
A mistake we see constantly is reading the wind as the direction it is blowing towards. Aviation wind is reported as the direction it comes from. Our explanation of decoding a METAR and comparing its wind with runway headings covers gusts and variable winds as well.
Raw METAR wind direction is referenced to true north, while runway designators use magnetic direction. A simulator can handle that conversion internally. When choosing manually, magnetic variation matters most when the wind falls near the crossover point between two possible runways.
How can I predict which runway the simulator will use?
You can usually predict the assigned runway by checking the airport’s surface weather and then confirming its operating configuration.
- Read the destination surface wind. Use the airport’s latest weather or ATIS, not winds at cruising altitude or an old forecast.
- Convert each runway number into an approximate heading. Runway 18 is about 180°, runway 04 about 040° and runway 31 about 310°.
- Compare the wind direction with each runway. The smallest angular difference normally identifies the strongest headwind candidate. Consider gusts and crosswind limits, not direction alone.
- Check ATIS and ATC. These reveal the actual arrival and departure configuration. Our guide to how simulator ATC creates and changes runway assignments explains why the controller may choose a less obvious runway.
- Confirm that the runway suits the aircraft. Check length, surface, obstacles and approach availability. An ATC clearance does not prove that a short runway is suitable for a heavy or fast aircraft.
Light or variable wind makes the result less predictable. Simulators may then use an airport’s default flow, the longest runway, an established AI traffic direction or whichever runway their airport data gives priority.
Why does ATC assign a runway with a tailwind?
A small tailwind assignment usually means the airport is maintaining an established traffic flow, the weather has changed, or the simulator is applying a tailwind tolerance before reversing operations.
- Weather changed after the assignment: ATC may retain the original approach while aircraft are already lined up or established.
- Weather sources disagree: Injected weather, the displayed ATIS and the ATC engine may update at different times or use different nearby reporting stations.
- The airport has a default configuration: Calm or marginal winds can trigger a preferred runway rather than constant switching.
- Scenery and airport data conflict: A visually closed runway may still be marked usable in the airport data, particularly when two airport packages overlap.
- The flight plan contains an old approach: Some ATC systems continue using the planned runway until the approach or clearance is changed.
First obtain a fresh ATIS and verify the actual surface wind. Then request another runway or approach if the simulator permits it. If the problem persists at one airport, check for duplicate scenery packages or airport data that incorrectly marks a runway as open.
Do not continue an approach that exceeds the aircraft’s permitted wind component merely to satisfy default ATC. Request a safer runway, discontinue the approach or go around.
Does the STAR or flight plan choose the active runway?
A flight plan or STAR can influence the expected arrival, but it does not normally determine which runway the airport has in use.
Many STARs end at a common arrival point and then connect to runway-specific transitions or approaches. The sensible order is to identify the likely airport flow, select the appropriate arrival and update it if ATC assigns something else. See our guidance on matching a STAR to weather, ATIS and the expected arrival runway.
Selecting a runway in the FMC or GPS does not command the airport to use it. It prepares the aircraft’s route. Built-in ATC may sometimes follow a runway already embedded in an imported plan, but the clearance remains the controlling assignment.
What if the airport has no ATC?
At an uncontrolled airport, there may be no formally selected active runway at all. Choose the runway offering a safe wind component while considering length, surface, terrain, published procedures and traffic already in the circuit.
In multiplayer or around AI traffic, avoid turning directly against an established flow solely because another runway offers a slightly better headwind. With calm winds and no traffic, use the airport’s preferred runway if the simulator or airport information provides one; otherwise choose the safest practical option for the aircraft.