Has this ever happened to you? Your flying along in your B-17 or Lancaster, fairly high up there. There is NOBODY around. Your on auto pilot, straight and level, not stressing the airframe in anyway, then Crunch, no bullet or cannon shell "hit sound" but your wing is gone, your on fire, you bail out "so and so shot you down". you look around in your chute, no enemy planes around, no "engine sounds" can be heard from your chute. You ask Mr so and so about it on private ( we will cal mr. so and so er13 ) no response.
Makes ya go Hmmm , don't it?