Fix a Navigraph flight plan that will not load in X-Plane 12, including .fms folders, AIRAC mismatches and “error prepping navigation data”.
A Navigraph flight plan usually will not load in X-Plane 12 because it was exported in the wrong format or folder, its AIRAC cycle does not match the simulator or aircraft, or a custom FMS expects another import method. Use an X-Plane .fms export in Output/FMS plans, then load and activate it in the cockpit.
How do I load a Navigraph flight plan correctly?
Export the route as an X-Plane .fms file, place it in the active X-Plane 12 installation and open it through the aircraft's avionics.
- Choose the X-Plane export format. Use the
.fmsoption. Some Navigraph interfaces may label the compatible format for X-Plane 11; X-Plane 12 can read that standard. A PDF chart, route string, Microsoft.plnfile or an aircraft-specific company route cannot be converted merely by renaming it. - Save it in the active installation. The standard location is
X-Plane 12/Output/FMS plans/. Check for an older X-Plane installation, a demo copy or a second X-Plane 12 folder receiving the export by mistake. - Inspect the complete filename. It must end in
.fms, not.fms.txt. Hidden filename extensions cause this more often than most users expect. On operating systems with case-sensitive paths, the folder name and location must also be exact. - Load it from the cockpit. Use the flight-plan catalogue, route page, co-route field or aircraft-specific import control. Copying the file does not activate it. If the aircraft was already running, refresh its route list or reload the aircraft.
- Add procedures in the avionics when necessary. Many importers handle the en-route legs but expect the pilot to select the runway, SID, STAR, transition and approach from the installed cockpit database.
- Compare the AIRAC cycles. The route, X-Plane and any separate aircraft database should contain compatible navigation data. A mismatch can reject waypoints or procedures, although it does not normally make a correctly placed file disappear from the catalogue.
- Check the add-on's own instructions. A custom Airbus, Boeing or other complex aircraft may use a private route folder, EFB transfer function or company-route format instead of X-Plane's standard loader.
Our standard X-Plane 12 flight-plan folder and activation walkthrough covers the complete simulator-side process.
What does each Navigraph loading problem mean?
The point at which loading fails usually identifies the cause more reliably than reinstalling everything.
| Symptom | Most likely cause | First check |
|---|---|---|
| Plan is absent from the cockpit list | Wrong folder, X-Plane installation or filename extension | Confirm Output/FMS plans and reveal the complete filename |
| Plan appears but is rejected | Unsupported file syntax, aircraft-specific importer or missing waypoint | Try the same file in a default X-Plane aircraft |
| Only en-route legs load | Procedure-import limitation or AIRAC mismatch | Select the SID, STAR and approach in the cockpit |
| It works in a default aircraft but not an add-on | The add-on uses another format, folder or navigation database | Use the aircraft's documented import method |
| Route is visible in Navigraph Charts but not the FMS | Charts and cockpit avionics are separate systems | Export the route or use a transfer feature explicitly supported by the aircraft |
| “Error prepping navigation data” appears | The AIRAC package could not be downloaded, unpacked or written | Check the data-manager mapping, storage and folder permissions |
How does Navigraph FMS Data Manager work with X-Plane 12?
Navigraph FMS Data Manager updates navigation databases; it does not copy a route from Navigraph Charts into the aircraft.
For X-Plane 12, the manager's mapping must point to the installation you actually launch, with the simulator's third-party navigation data placed under X-Plane 12/Custom Data/. If several X-Plane copies exist, confirm the full target path rather than relying on automatic detection.
A sophisticated add-on may keep its own database and therefore require an additional supported mapping. Updating only Custom Data does not guarantee that every third-party FMS is using the same cycle. Our X-Plane 12 Navigraph installation guidance explains the distinction between simulator data, aircraft data and flight-plan files.
How do I fix “error prepping navigation data”?
“Error prepping navigation data” is an installation-stage failure, not evidence that the route itself is malformed.
- Identify which program reports it. An error in FMS Data Manager before X-Plane starts concerns downloading, unpacking or installing AIRAC data. An X-Plane startup error points instead to files already present under
Custom Data. A cockpit message after selecting a route is a separate import problem. - Close X-Plane before updating. The simulator or an aircraft component may have navigation files open, preventing the manager from replacing them.
- Verify the mapping. Make sure the destination belongs to X-Plane 12 rather than X-Plane 11, a backup or another copy. Correct a stale mapping before retrying.
- Check storage and write access. Both the destination and the operating system's temporary-file location need free space. Confirm that the signed-in user can modify the X-Plane folder and that security software has not quarantined or blocked the downloaded package.
- Retry with a fresh package. Use the manager's own remove, repair or reinstall function where available. Do not combine files from different AIRAC downloads or overwrite X-Plane's bundled data under
Resources/default data. - Isolate a broken custom installation. If X-Plane itself fails while preparing navigation data, back up the third-party files in
Custom Data, move them out temporarily and start X-Plane with its bundled database. If it then starts normally, reinstall the custom AIRAC package cleanly.
What does MISM 430 mean?
MISM 430 is not a standard X-Plane 12 FMS route-rejection message. When it appears alongside a navigation-data preparation failure, retain the exact application name, package and surrounding log text: the number alone does not identify a bad waypoint or AIRAC cycle.
Treat it first as an installer or file-preparation problem by checking the target mapping, permissions, temporary storage and package download. Editing the .fms route will not fix an error raised before the simulator or aircraft attempts to read that route.
Why are Navigraph waypoints, SIDs or STARs missing?
Missing waypoints and procedures normally mean the aircraft is reading different or older navigation data from the data used to create the route.
Compare the AIRAC cycle shown by Navigraph with the cycle reported by the aircraft's FMS, database status page or EFB. Check X-Plane separately because a custom aircraft can maintain its own database. Do not edit a cycle number in the flight-plan header to make it appear to match; that does not install the absent fixes or procedures.
If only a SID, STAR or approach is missing, select it manually from the cockpit database after choosing the active runway and transition. If individual fixes are rejected as “not in database”, use our AIRAC and unsupported-waypoint checks before rebuilding the affected legs.
How can I tell whether the aircraft is causing the problem?
Load the same .fms file in a default X-Plane aircraft equipped with a standard GPS or FMS.
If it appears there, the file, extension and standard folder are valid. Concentrate on the add-on's route format, private database, filename restrictions or EFB import procedure. If the default aircraft also cannot see it, return to the export format, full filename and Output/FMS plans path.
Why is the route visible in Navigraph Charts but absent from the FMS?
A route displayed in Navigraph Charts is not automatically inserted into X-Plane's cockpit avionics.
Charts provides route planning, chart display and moving-map functions. Simlink can supply aircraft position to Charts, but that connection alone does not transfer a flight plan into the FMS. Unless the chosen aircraft explicitly supports direct route transfer, export the X-Plane file and import it through the cockpit; a downloaded chart PDF is only a reference document.
What if the plan loads but the autopilot ignores it?
A loaded route that the aircraft will not follow is an avionics or guidance problem rather than a Navigraph export failure.
Check that the route has been activated or executed, the next leg is active, no unresolved discontinuity remains, and the navigation source is GPS/FMS rather than VOR or localiser. The appropriate lateral mode must then capture the route. For Garmin-equipped aircraft, follow our G1000 active-leg, GPS-source and NAV-capture checks.