We can account for just about every allied aircraft that the Germans returned to flying condition and they were all given a stammkennzeichen which was prominently displayed along with national markings and other special markings. I hesitate to say every aircraft because we're talking Luftwaffe seventy years ago, but I'm as sure as anyone can be that all the B-17s and B-24s returned to flight can be accounted for. They were not that numerous. Why would they be?