Abstract: A process and device for detecting the current phase of operation of a system with multiple phases of operation. According to the invention, the operation is partitioned into a set of phases (I to X) from which is chosen a reference phase (I). The set of possible switches to the other phases is determined for each phase. And, a set of parameters is defined for each of the switches, the set of parameters being characteristic of the switch. The sets of parameters are continuously detected. The chain of switches actually involved is determined on the basis of the reference phase (I) with the aid of variations in the parameters, and the current phase of operation is deduced from the chain of switches. Although the invention is applicable to numerous systems, one such system to which it is applicable is the operation of a transport airplane.