A method and system for assisting guidance of an aircraft along a runway approach axis. The method includes acquiring a position deviation between a current position of the aircraft and the approach axis, determining an angle between a longitudinal axis of the aircraft and the approach axis, and determining a lateral offset of the trajectory of the aircraft likely to result from a maneuver of alignment of the longitudinal axis of the aircraft with the runway during the landing of the aircraft. A lateral trajectory correction is computed as a function of the lateral trajectory offset. This position deviation is corrected by adding the lateral trajectory correction to it. This position deviation is transmitted to the device for guiding the aircraft.