The movie concludes with George Peppard crashing a test monoplane. The shot is from James Mason's office, looking out over the airfield. We hear the sound of the diving plane, but do not see it. After the camera has been focused on the field for a few seconds, we see a large explosion, which is meant to represent the crashing plane. The falling plane is missing. From the position of the shot, we should have seen the crashing plane.
The number of the Berlin hotel room Bruno Stachel stays in the night before he is to be awarded the Blue Max is '22', which equals the number of planes he has shot down. He needed only 20 to win the award, but he had to shoot down two more in order to make up for Willy's kills that he claimed as his own earlier in the film.