Method and device for guiding an aircraft. The device (1) for guiding an aircraft at least over an intermediate trajectory between a first flight trajectory for a low-altitude flight and a second flight trajectory which starts at an initial point, and from which trajectory a tactical landing is carried out, comprises means (9) for determining a point of transition which lies on the first flight trajectory which represents the start of the intermediate trajectory, and which corresponds to the point where the aircraft must exit the first flight trajectory so as to reach the initial point under predetermined flight conditions, and the second means (13A, 13B) which use the point of transition to aid the guidance of the aircraft between the first and second flight trajectories.