There's a long-standing concern that stealth aircraft appear as a void against background radiation: https://bulgarianmilitary.com/2020/07/10/russia-received-te

There's a long-standing concern that stealth aircraft appear as a void against background radiation: https://bulgarianmilitary.com/2020/07/10/russia-received-technology-revealing-invisible-stealth-aircraft/ https://bulgarianmilitary.com/2020/07/10/russia-received-tec... More info: https://www.thedrive.com/the-war-zone/30100/no-passive-radar-isnt-stealth-ending-magic-people https://www.thedrive.com/the-war-zone/30100/no-passive-radar...