The method involves characterizing a flight phase of an aircraft. A determination is made whether the aircraft is authorized to lose altitude (S113). A prohibited flight envelope is determined (S114). A set of prohibited vertical speeds of the aircraft for given altitudes is defined according to the characterized flight phase of the aircraft. A descent anomaly of the aircraft is detected (S115) according to current vertical speed and altitude of the aircraft in relation to the determined prohibited flight envelope. An independent claim is also included for a system for detecting descent anomaly of an aircraft.
