The primary cockpit displays include a left- and right-side cathode-ray tube display, referred to as the DDIs, and the heads-up display (HUD). The DDIs and HUD are generally used to display primary flight condition information such as airspeed, altitude, altitude rate, attitude, heading, etc. Other flight conditions displayed include angle of attack (AOA), Mach number, and load factor. The HUD also provides primary flight condition information to the pilot without having to refer to the DDIs. Select flight controls information also can be presented on the HUD. The twenty pushbuttons located on the periphery of each DDI are used to select a variety of displays for pilot interrogation of F-18 systems. These displays are pilot selectable and menu driven.