A display generation system that is able to generate display signals for an underlay image with at least one embedded safety pattern and display images for an overlay image. The display generation system and method are able to determine whether there are any anomalies or graphical errors when an overlay display generated by the system or generated by some other system is displayed simultaneously with the underlay image with the embedded safety pattern. The display generation system uses the embedded safety pattern to detect the occurrence of anomalies in the simultaneous display and uses information from its own generated overlay image to detect graphical errors in the simultaneous display. Flight display systems for aircraft can use the display generation system and method of the present invention to display an underlay image depicting geographical scenery in the vicinity of the aircraft while on the ground, during takeoff or in flight. The underlay image is displayed simultaneously with an overlay image depicting standard graphics of a flight display system.