an aircraft display communicates three dimensional lateral information to a pilot of the aircraft . an extended course centerline symbol and lateral deviation marks indicate lateral deviation from a desired course along with approximate altitude and distance - to - go information to the pilot . the course centerline extends toward a vanishing point near the horizon line of the display . the centerline symbol swings laterally across the display responsive to changes in lateral deviation of the aircraft such that an intuitive perspective view is provided to the pilot . lateral deviation marks provide precise lateral deviation information to the pilot . the display is adaptable to all phases of flight , but is particularly useful during the approach phase of flight . the preferred embodiment is on a head - up display for instrument flight conditions .