An example of the 737's leading-edge technology is a sophisticated system called Head-up Display or HUD. Although HUD has been used on military aircraft for several years, the 737 is the only large commercial jetliner produced today with this capability. HUD uses a transparent glass display positioned between the pilot's eye and the flight deck window to show critical information such as airspeed, altitude, attitude and flight path. During takeoffs and landings, an image of the runway is superimposed over the actual view out the window.