A visual aid for the pilot of an aircraft approaching to land on an aircraft carrier comprises a series of lights (9) embedded along the landing deck and controlled in response to pitch and heave of the vessel so that the light(s) illuminated at any time indicate a visual aim point which is stabilised with respect to a specified glideslope (5) onto the vessel irrespective of such vertical excursions of the vessel. It is used in conjunction with a marker on a head up display or helmet mounted display for example so that registry of the marker with the illuminated light at any time indicates that the aircraft is on the correct glideslope.