MIflyer
Captain
I guess they all had windows that could be closed, which you certainly would need if you were ferrying them somewhere. But I wonder if the windows were even installed on combat missions. I recall reading that for one of the Aphrodite missions an extra B-17 showed up and they were highly suspicious that it might be a captured one operated by the Luftwaffe. So the mission commander gave the escorting fighters orders to shoot it down if anyone started manning the guns or opening the waist windows and to follow it after the left the target area and shoot it down if headed toward the European continent. When he got back to base 8th AF HQ called and said that they got a B-17 and come along to watch. He replied that it was a very good thing that no one needed a bit of fresh air and opened the windows. Someone was supposed to tell him about the B-17 with sightseers but forgot somehow.