A method and apparatus for displaying an image to an aircraft pilot (20). The method comprises: displaying, by a display (24), to the pilot (20), an image comprising guidance symbology (34) for use by the pilot (20) when landing the aircraft (2), the position of the guidance symbology (34) on the display (24) being dependent upon an output of an INS of the aircraft (2); providing, to a processor (26), an indication that the INS output is incorrect; determining, by the processor (26), a further value for the INS output and a specification of further guidance symbology (40); and displaying, by the display (24), to the pilot (20), an image comprising the further guidance symbology (40). The position on the display (24) of the further guidance symbology (40) relative to that of the guidance symbology (34) is dependent upon the difference between the further value and the incorrect INS output.