The expiration of the Provisional Registration of my aircraft is near and I still do not have the legal document registered at the Registro de Bienes Muebles de Madrid. Is it possible to extend this deadline?

Yes, it is possible to issue an extension of 45 days to the validity of the Provisional Registration at the request of the interested party. In the following link you can download the MOD 3 for requesting an extension: https://sede.seguridadaerea.gob.es/sede-aesa/catalogo-de-procedimientos?title=Registro+de+Matr%C3%ADcula+de+Aeronaves+Civiles&items_per_page=25