Find out why your FMC won't import a flight plan in FSX and fix format, folder, navdata, waypoint and route-activation errors.
An FSX FMC usually refuses a flight plan because the file is in the simulator’s .PLN format, while the add-on expects its own company-route format and folder. A navigation-data mismatch, invalid waypoint, unsuitable filename, or a route that was loaded but not activated can produce the same symptom.
Why doesn’t every FMC read an FSX flight plan?
FSX has no universal FMC import system. Its built-in Flight Planner saves an XML-based .PLN file that the simulator’s GPS and ATC understand, but a third-party aircraft may use a separate FMC, route format, storage folder and navigation database.
Some aircraft can import the active FSX flight plan. Others accept only company-route files exported specifically for that aircraft, while simpler FMC gauges may offer no file import at all. Renaming a .PLN file with another extension does not convert its contents.
Our guide to how FSX creates and saves .PLN flight plans explains the simulator side of this distinction.
What does the FMC error or symptom mean?
| Symptom | Likely cause | What to check |
|---|---|---|
| The route appears in the FSX GPS but not the FMC | The FMC does not read active FSX plans, or import has not been requested | Check which import method the aircraft supports |
| The route is absent from the saved-route list | Wrong folder, format, filename or file extension | Verify the aircraft’s documented route folder and enable file extensions in Windows |
NOT IN DATABASE or INVALID ENTRY | The FMC database does not contain a waypoint, airport, runway or airway | Compare the plan’s navigation data with the FMC database |
| Only the departure and destination load | Unsupported procedures, coordinates, user waypoints or airway syntax | Test a basic route without SIDs, STARs or custom points |
| The route is on the LEGS page but LNAV will not follow it | The route is not active, contains a discontinuity, or the aircraft is not configured for FMC guidance | Activate and execute the route, then check the active leg and autopilot mode |
How do I fix an FMC that will not import a flight plan?
Fix the import by proving the plan in FSX, then matching the FMC’s required format, folder and navigation database.
- Identify the aircraft’s import method. Check whether its FMC accepts an active FSX plan, a company-route file, or manual route entry only. FSX and FSX: Steam Edition do not determine this; the aircraft add-on does.
- Load the plan in FSX first. Open it through the built-in Flight Planner and confirm that the route appears on the map or GPS. If FSX itself rejects the file, resave it as a fresh
.PLNbefore troubleshooting the FMC. - Use the correct format and folder. An FMC route often belongs in an aircraft-specific route directory, not the folder selected by FSX’s Save dialog. Export directly to the aircraft’s supported format where possible. Check that Windows has not silently created a filename such as
ROUTE.ext.txt. - Try a minimal test route. Use two airports known to exist in the FMC, one conventional en-route fix and no procedures, coordinates or user-created waypoints. If that imports, add the remaining route sections one at a time to expose the rejected item.
- Use a simple route name. As a diagnostic, choose a short name containing only basic letters and numbers, with no spaces or punctuation. Filename and route-name limits vary between add-ons, so follow the aircraft’s rules rather than assuming the full filename belongs in the company-route field.
- Import, inspect and activate. Confirm the origin, destination and legs after loading. Resolve discontinuities deliberately, select any required departure or arrival inside the FMC, then activate or execute the route using the aircraft’s normal procedure.
Why does the FMC reject only some waypoints?
Individual waypoint failures usually mean that the route and FMC were built from different navigation databases. FSX scenery data and an add-on FMC’s AIRAC data are separate, so updating one does not automatically update the other.
A recently changed identifier, runway, airway or procedure may therefore exist in the route file but not in the FMC. Generate the plan against matching data where possible, substitute a waypoint the FMC recognises, or update the correct database if the add-on supports it. Our guide to FSX and add-on navigation databases explains which data must actually be updated.
Procedures are another common trap. Many FMCs work more reliably when the en-route portion is imported and the SID, STAR and approach are selected inside the FMC from its own database.
Why is the route visible in the GPS but not the FMC?
The FSX GPS and a third-party FMC can display completely independent flight plans. Loading a .PLN into FSX makes it available to the simulator’s GPS and ATC, but it reaches the FMC only if that aircraft includes an explicit FSX-plan import function.
If no such function exists, use the aircraft’s company-route format or enter the route manually. Saving extra copies of the same .PLN in different folders will not add compatibility.
Why won’t LNAV follow the imported route?
An imported route is not necessarily an active route. The FMC must have a valid origin, destination and active leg; the route must be executed; and unexpected route discontinuities must be resolved before LNAV can follow it.
The aircraft may also require position initialisation, aligned navigation systems, the correct flight-director or autopilot state, and FMC guidance selected as the navigation source. These details vary by aircraft. For a representative workflow, see the complete FMC route-entry and activation sequence for a Boeing 737.