Yehudi lights are lamps placed on the underside or wing leading edge of an aircraft to raise luminance, to disguise the aircraft against the background sky. The technique was successfully employed in World War II by RAF Short Sunderland aircraft in attacks on U-boats.
In 1945 a Grumman Avenger with Yehudi lights got within 3,000 yards (2,700 m) of a ship before being sighted. This ability was rendered obsolete by the radar of the time. Since the development of stealth technology, Yehudi lights have come under renewed interest.[1]