The invention relates to a synchronization of a dual avionic and non-avionic system. Various methods for regulating and/or for integrating avionic systems with non-avionic or open systems are described. Developments of the invention describe in particular various methods for synchronizing data via a sharing space, methods for modifying the data, human-machine interactions, steps of optimizing calculations and bandwidth, of determining alerts relating to the risks associated with calculation differences, and mechanisms for securing the secured storage space. Software and system aspects are described (EFB and FMS).