Revealing mistake: The B17 that crash lands in the beginning appears quite realistic, until during a head on shot when you can see daylight through the clear nose from a window in the back of the plane. This shows it to be model as in the real plane bulkheads would block this from happening.
Revealing mistake: When C-Cup's nose gets clipped and the guy falls out, it is most obviously a doll/dummy falling out.
Chosen answer: It would seem that every plane's Norden bombsight would drop from different angles, etc., each designated for a common target. So, 2 planes could be higher, lower, ahead or behind the target and each hit the target, if the bombadiers had an accurate fix on the target.