The device (1) comprises means (6) for determining an auxiliary flight plan corresponding to a lateral revision of the current flight plan, at least over a low altitude flight section, means (3) for automatically determining at least one decision point which indicates the last position of the aircraft along the current flight plan, where the auxiliary flight plan can still be activated, so as to allow the aircraft to overfly the terrain in complete safety by following the auxiliary flight plan, under the same flight conditions as those envisaged for the current flight plan, means (9) for automatically presenting at least the decision point to a pilot of the aircraft, and means actuatable (13), allowing a pilot to activate the auxiliary flight plan, so as to carry out the lateral revision of the current flight plan.