Well yeah, that was my first thought. They coat a part of the plane with a radioactive isotope. It would have to be a lot of the stuff to ionize enough air around the part to hide it from radar. Considering that the plane is flying, and the air around it doesn’t sit still I would guess that in certain frequencies it would be bright as the sun. If this thing works as stated I wouldn’t get close to that thing without a decent amount of concrete between us.