Fix an FMC 'not in database' error by checking identifiers, AIRAC cycles, entry syntax and aircraft navdata with clear, platform-aware steps.
An FMC NOT IN DATABASE error in a flight simulator means the identifier or route element you entered cannot be found—or is invalid in that field—in the aircraft’s navigation database. Check spelling and entry format first, then compare AIRAC cycles and update the aircraft’s navdata rather than assuming scenery is at fault.
What does “NOT IN DATABASE” actually mean?
This is a database lookup or entry-context failure, not evidence that the FMC itself is broken. The unit either cannot locate the identifier or does not permit that type of entry on the selected page. Depending on the simulated FMC, the same problem may instead produce INVALID ENTRY or a similar scratchpad message.
General flight simulators can contain several independent navigation-data layers. The simulator, an add-on aircraft, ATC and an imported flight plan may not use the same database. An airport appearing in the scenery therefore does not prove that the aircraft’s FMC knows about it.
| Rejected item | Most likely causes | Best first check |
|---|---|---|
| Airport | IATA code used instead of ICAO, renamed identifier or airport absent from the database | Enter the published ICAO identifier |
| Waypoint or navaid | Typing error, retired or renamed fix, or route built against another AIRAC cycle | Compare the identifier with the source route and active cycle |
| Airway | Entered in the wrong field, wrong entry order or exit waypoint not connected to that airway | Check the VIA/TO sequence |
| SID, STAR or runway | Procedure-cycle mismatch, runway renumbering or wrong transition | Select it through the departure or arrival page |
| Latitude/longitude | Coordinate syntax unsupported by that FMC | Use the aircraft’s documented coordinate format |
| Imported or saved route | Old procedure, incompatible route format or unsupported route-string token | Enter the failing segment manually |
How do I clear the FMC error?
- Identify the exact rejected entry. Note the identifier and the page on which it failed before clearing the scratchpad message. Clearing
NOT IN DATABASEremoves the warning; it does not correct the route. - Check the identifier and field. Airports normally require ICAO rather than IATA codes. Do not enter
DCTas though it were a waypoint, and place airways in the airway orVIAfield rather than the waypoint field. Coordinate syntax varies substantially between FMC types. For Boeing-style units, our guide to the correct 737 route-page and airway-entry sequence covers the usual field and order mistakes. - Isolate the failure. If one fix fails while surrounding fixes work, suspect its spelling, status or AIRAC cycle. If the waypoint works as a direct entry but fails through an airway, the active database does not connect that waypoint to the airway as entered. If known airports and waypoints all fail, the navigation database may not have loaded at all.
- Compare AIRAC cycles. Look on the FMC’s IDENT, STATUS or database information page for its active cycle, then compare it with the route or procedure source. Matching cycles are not essential for every basic route, but a mismatch is the leading suspect when a renamed waypoint, new runway or revised procedure is rejected.
- Update the database the aircraft actually reads. A mistake we see constantly is updating the base simulator while an add-on FMC retains a separate, older database. For the relevant platform, follow the correct process for identifying and updating Microsoft Flight Simulator navdata layers, aligning Prepar3D add-on FMC navdata and checking its active cycle, or completing a FlightGear AIRAC installation and navigation-cache rebuild. In X-Plane, many aircraft read the simulator’s
Custom Dataset, while others maintain aircraft-specific data. - Reload the aircraft after updating. Many simulated FMCs read their database only when the aircraft loads. Restart or reload it, confirm the displayed cycle, and rebuild a navigation cache only when the simulator’s documented update process requires it. Deleting unrelated caches or scenery indexes can create additional problems.
- Re-enter stale routes and procedures. A saved company route can retain identifiers from an older cycle. Delete the failing segment, select the current SID or STAR from the FMC’s own pages, and rebuild that portion rather than repeatedly importing the same file.
Why did the error start after a navdata update?
An update can expose an old route or leave different navigation-data layers out of step. A procedure may have been renamed, a fix withdrawn, an airway connection changed or a runway renumbered while the saved plan still refers to the previous coding.
Use the procedure offered by the updated FMC rather than rolling back solely to preserve an old route. If every entry fails after an update, verify that the files were installed for the correct simulator and aircraft, then confirm that a valid cycle appears on the FMC’s database page.
Why does the waypoint work in another aircraft?
Two aircraft in the same simulator can use completely different databases. A default aircraft may read simulator-wide navdata while a detailed add-on uses its own files, so acceptance in one cockpit does not prove that another aircraft has the same cycle or coverage.
Can I enter a missing waypoint manually?
You can create a user waypoint from verified coordinates if the FMC supports it and only an en-route fix is missing. Follow that aircraft’s coordinate format exactly; formats are not interchangeable between Boeing, Airbus and other FMS implementations.
A user waypoint does not restore airway connectivity or the coded legs, turns, holds and altitude or speed constraints belonging to a SID or STAR. Do not approximate a missing procedure by typing a string of fixes. Install compatible navdata or select the current procedure from the FMC instead.
Will reinstalling airport scenery fix it?
Reinstalling visual scenery usually will not fix NOT IN DATABASE. Scenery controls what the airport and runways look like, while the FMC reads navigation records from the simulator or aircraft database.
If the runway shown outside differs from the one offered by the FMC, compare the scenery and navdata eras and choose a procedure that exists in the loaded database. Only repair a simulator navigation-data component when the aircraft genuinely reads it; reinstalling an unrelated airport add-on will not add a missing FMC waypoint.