An autopilot system comprising an onboard unit. The onboard unit has a plurality of sets of sensors that are redundant and mutually independent, together with a plurality of calculation channels, each calculation channel being connected to the sensors of one of the sets of sensors and receiving data coming from the sensors. A supervisor is connected to the sensors of a set of sensors, the supervisor having the function of coupling at most one of the calculation channels to the control members, the supervisor having the function of decoupling the coupled channel from the control members in the event that the current behavior of the aircraft departs from predetermined predicted behavior.