An ACARS message communications system including at least one on-board piece of equipment harbouring an application adapted for transmitting and/or receiving ACARS messages, and a router adapted for routing, via a plurality of subnetworks, ACARS messages from and/or to the application. The piece of equipment and the router are connected to an AFDX network and the application is adapted for dynamic registration at the router, via the network, the router only routing the messages if the application is actually registered thereat.