Why are you not allowed on the plane from Spain to Mexico?

I was not allowed to board the plane from Spain to Mexico because my FM card was overdue and there was no extension, which meant that the FM card had expired. Holding a valid tourist or business visit visa (FMM), whether a temporary resident (RESIDENTE TEMPORAL) or a permanent resident (PERMANENTE) visa card (FM), you can enter and exit multiple times. You only need to fill out an exit card when leaving the country. Registration form is enough. However, Spain is not allowed to board the plane to Mexico because although the FM card is held, it has not been extended, which means that the FM card has expired and needs to apply for a permanent exit permit (Permis de Salida definitiva) at the immigration bureau. This way you can board the plane smoothly.