Why does simulator ATC assign unrealistic routes or runways?

Simulator ATC assigns unrealistic routes or runways when its filed flight plan, weather, navigation database or airport data differ from the route in the aircraft’s FMS. Simplified controller logic can then issue stale waypoints, awkward vectors or unsuitable runways. Synchronising those data sources fixes most cases; the rest are ATC limitations.

This is a general simulator issue affecting built-in, offline ATC in Microsoft Flight Simulator 2020 and 2024, FSX, Prepar3D and X-Plane. The details vary by simulator and aircraft, but ATC can act only on information exposed to it; our explanation of the flight-plan, weather and airport data available to simulator ATC explains that boundary.

Is a different route or runway necessarily unrealistic?

No: a route or runway that differs from the FMS can still be operationally plausible.

Real controllers issue direct routings, radar vectors, holds, runway changes and amended arrivals for traffic, weather or airport flow. A small tailwind may also be accepted within local and aircraft limits. Suspect a simulator problem when ATC repeatedly returns you to completed fixes, vectors you away from the destination, assigns a missing runway or creates an approach that cannot be flown safely.

Why does ATC’s route disagree with the FMS?

ATC and the FMS usually disagree because they are following two separate copies of the flight plan.

A mistake we see often is filing one route in the simulator planner and then loading or editing another in the cockpit. Built-in ATC continues to use the simulator-level plan, while the autopilot follows the active route in the FMS. Selecting Direct-To, changing a STAR or entering a new runway in the aircraft does not automatically amend ATC’s copy.

• Separate plans: The simulator planner contains one waypoint sequence while the aircraft FMS contains another.
• Unexecuted changes: A route has been entered in the FMS but has not been activated or executed.
• Procedure overlap: The last en-route fix is duplicated as the first STAR or approach fix, producing a loop or reversal.
• Runway or transition mismatch: The selected STAR, transition and approach do not connect logically.
• Different navigation data: The simulator, aircraft and airport scenery disagree about waypoint locations, procedure coding or runway identifiers.
• Vectors or manual legs: The procedure expects radar vectors, but the simulator tries to interpret it as a continuous route.

Runway changes are especially troublesome because changing only the approach can leave the original arrival or transition in place. Our guide to how simulator ATC handles SIDs, STARs and runway transitions covers that relationship in more detail.

What do the common symptoms indicate?

What does 270/12, 270:12 or 270-12 mean?

In an aviation weather context, 270/12 means wind from 270 degrees at 12 knots; 270:12 and 270-12 are alternative display formats for the same information.

The wind comes from the west, so it generally favours a runway pointing approximately west, such as Runway 27. If the runway were aligned exactly with the wind, Runway 27 would have about 12 knots of headwind and the reciprocal Runway 09 would have about 12 knots of tailwind.

A coded METAR normally expresses this as 27012KT. Gusts might appear as 27012G20KT, meaning 12 knots gusting to 20. METAR directions use true north, while runway numbers approximate magnetic heading, so the numbers need not match exactly.

An assignment of Runway 09 with wind shown as 270/12 deserves checking, but it does not prove ATC is broken. The ATIS may be stale, another weather source may disagree, or the simulator may be enforcing an airport flow encoded in the scenery.

Why does simulator ATC select the wrong runway?

Simulator ATC selects an apparently wrong runway when its wind, airport configuration or suitability logic does not represent the conditions seen in the cockpit.

• Weather timing differs: Planning weather, live weather and ATIS may have been sampled at different times.
• The airport flow is simplified: Noise restrictions, terrain, preferred runway combinations and separate arrival or departure runways may not be modelled.
• Scenery is outdated: An airport package may retain an old, closed or renumbered runway.
• Navigation data do not match: The FMS may contain a procedure or runway identifier absent from the installed airport scenery.
• Aircraft suitability is poorly assessed: Some engines do not fully account for landing distance, aircraft category, runway width or required approach equipment.
• Traffic logic takes priority: Simplified AI sequencing may keep one runway active even when another appears more suitable.

In Microsoft Flight Simulator, mismatches between weather, scenery, the simulator plan and avionics can affect the runway and the vectors leading to it. We cover the platform-specific checks in our diagnosis of incorrect MSFS vectors, altitudes and runway assignments.

How do I fix unrealistic ATC routing and runway assignments?

Fix unrealistic assignments by choosing one authoritative plan, checking the wind and making the simulator-level route agree with the aircraft’s active route.

1. Decide which system has priority. Use the simulator’s supported planner as the authority when coherent built-in ATC clearances matter most. Use the aircraft FMS as the authority when accurate aircraft procedures matter more, accepting that you may need to cancel or ignore built-in ATC if it cannot share that route.
2. Verify the wind correctly. Read 270/12 as wind from 270 degrees at 12 knots. Compare the planner’s weather with the destination ATIS rather than assuming the runway chosen before departure remains active.
3. Compare the complete waypoint sequence. Check the simulator plan and every FMS LEGS page, not just the route line on the map. Look for omitted fixes, duplicate fixes, reversals and an old destination runway.
4. Rebuild incompatible procedures. Confirm that the final en-route fix, STAR, transition, approach and runway connect in that order. When the runway changes, remove the obsolete approach and transition before loading the replacement.
5. Synchronise later amendments. Where the simulator permits it, amend or refile its ATC plan after changing the route. Editing only the cockpit FMS leaves ATC on the old clearance.
6. Resolve genuine discontinuities. Close accidental gaps and duplicates, but retain a discontinuity that represents expected radar vectors until you have a valid onward clearance or intercept.
7. Align airport and navigation data. Remove duplicate airport scenery and update or disable packages containing obsolete runway layouts. Aircraft navigation data and scenery do not need identical release dates, but they must agree on the runway and procedure being used.
8. Request an alternative when supported. Ask ATC for another runway or approach before committing to the descent. If the simulator offers no suitable amendment, cancel built-in ATC rather than repeatedly altering only the FMS.
9. Recognise a logic limitation. If the filed route, active FMS plan, weather and airport data all agree but the same bad instruction persists, the remaining cause is probably the ATC engine itself.

Why is MSFS autopilot not following the flight plan?

In MSFS, an autopilot that does not follow the flight plan usually has the wrong lateral mode, navigation source or active leg; normal built-in ATC does not steer the aircraft.

1. Read the flight-mode annunciator. Confirm that the expected navigation mode—such as NAV or LNAV for that aircraft—is active, not merely armed. HDG mode follows the selected heading rather than the flight plan.
2. Check the navigation source. The flight director must use the FMS or GPS source for route tracking, not a VOR or localiser source. Names and indications vary between avionics suites.
3. Activate and execute the route. Make sure the intended flight plan is active and that any modified route has been executed. A route visible on a CDU is not necessarily the active route.
4. Inspect the active leg. Confirm that the next fix is sensible and lies ahead of the aircraft. Use Direct-To only when appropriate; repeatedly selecting it can hide an underlying route error.
5. Look for a discontinuity or vectors leg. The autopilot cannot follow a continuous path where the FMS has deliberately or accidentally left a gap.
6. Establish an intercept. Some systems will not capture a route when the aircraft is too far from the leg or approaching it at an unsuitable angle. Use heading mode to establish a reasonable intercept, then arm the correct navigation mode.
7. Check assisted-flight features. AI piloting or assistance options can override normal inputs. Disable them while diagnosing the aircraft’s own autopilot.

If the aircraft follows the displayed route while ATC calls a different waypoint, the autopilot is probably working and the two flight plans disagree. If both ATC and the route display are correct but the aircraft does not turn, concentrate on autopilot modes, source selection and leg activation.

How do I delete a route discontinuity in the PMDG 737?

In the PMDG 737, close a route discontinuity by moving the next intended waypoint over the gap on the CDU LEGS page, then review and execute the modified route.

1. Open the LEGS page. Find the ROUTE DISCONTINUITY and identify the waypoint immediately below it.
2. Select the next intended waypoint. Press its adjacent line-select key to copy that waypoint to the scratchpad.
3. Place it over the discontinuity. Press the line-select key beside the discontinuity position. This connects the preceding leg directly to the selected waypoint.
4. Review the new track. Check the LEGS pages and navigation display for an unexpected turn, route reversal or terrain conflict.
5. Execute only if correct. Press EXEC to activate the modification. If the proposed path is wrong, erase the modification rather than executing it.

Do not remove every discontinuity automatically. A discontinuity after a VECTORS or manual leg may be intentional: fly the assigned heading, then select the next fix or intercept the approach when cleared. Closing it early creates a direct track that may not match the procedure or ATC clearance.

Also remember that closing the gap in the PMDG FMC changes only the aircraft’s route. It does not update the flight plan held by MSFS built-in ATC, so ATC may continue issuing instructions based on the old route.

Should I obey a clearly unsafe simulator ATC instruction?

No: built-in ATC should never take priority over terrain clearance, aircraft limitations or a stable approach.

Maintain a safe altitude, reject an unsuitable runway, discontinue the approach or go around rather than following an obviously unsafe vector or descent. Cancelling or ignoring offline ATC may break later clearances, but that is preferable to continuing an unsafe simulated flight path. Our practical guidance for handling unsafe simulator clearances explains how to separate a harmless ATC limitation from an instruction that should be refused.

When flying with a human controller, query the clearance or state that you are unable instead of silently departing from it. Human-controlled ATC and specialised ATC add-ons do not necessarily share the limitations described here.