Yehudi lights are lamps of automatically controlled brightness placed on the front and leading edges of an aircraft to raise the aircraft's luminance to the average brightness of the sky, a form of active camouflage using counter-illumination. They were designed to camouflage the aircraft by preventing it from appearing as a dark object against the sky. Yehudi lights were unused in the war and were made obsolete by advanced postwar radar. With 1970s improvements in stealth technology, they again attracted interest.