I read one fascinating account of how a badly wounded B-17g was separated from it's formation and losing height rapidly. The turret's were out of ammo and the waist gunners either wounded or tending to other wounded crew. They are flying over Denmark on the way back from a mission over Germany.
Suddenly from out of nowhere an FW 190 appears about fifty feet from the port wing, he moves in closer and it is clear that he is looking the B-17 over. The 190 dive underneath and come up on the other side staying about fifty feet away. A couple of times he closes quickly to within about twenty feet before backing off. He then returns to the port side and pulls the same stunt. Finally the pilot has enough and orders one of his men to man the mid upper turret. The fighter pilot see's this and backs off waggling his wings like a lunatic on the way out. They see no more of him.
The B-17 made it home, she crossed the English coast about 100 feet above the deck and somehow made it home.
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In 1982(ish) the pilot of the B-17 is reading a magazine article about the Luftwaffe when he realises that what he is reading is a description of what happened to him and his crew back in '44. He manages to get in contact with the German pilot and they agree to meet up.
What had happened was that the German pilot had landed back at base after a successful interdiction mission. He was in the process of taxiing when the tower informed him that the sound of a bomber could be heard passing overhead, he immediately scrambled and flew an intercept. He broke out of cloud less than 100 feet from the bomber and was literally staggered by how much damage the thing had taken and was still flying. He could see blood flowing from the bomber as if it was wounded and not the men in it.
Although he had the ammunition and fuel to finish her off he decided that he couldn't bring himself to do it. In that moment the American crew became Men, not Enemies. He attempted to turn the bomber first towards a German airfield and then a neutral Swedisih airfield as he felt that she couldn't possibly fly back to England. When he realised that this would not work he saluted her and flew home. He made up a story about jammed guns or something to defend himself and spent the next 18 months frightened that someone had seen him because he would have been court-marshalled and at the very least(

) shot.
The two men met up every year until at least 1994 when the book I read was published.
Will