The general field of the invention is that of the methods for three-dimensional graphic representation of at least one landing runway on a display device of an onboard display system for aircraft, said graphic representation being displayed in a synthetic of an outside landscape, said runway comprising a coloured rectangular form, an outline surrounding said form and markings the position of the aircraft in relation to said runway being known in a horizontal plane with a first accuracy and in a vertical axis with a second accuracy. When the first accuracy is above a first threshold and/or when the second accuracy is above a second threshold, the appearance of the rectangular form or of the outline or of at least one marking is modified.