B-17
Sidebar: the B-24 was somewhat more likely to be shot down, as it had a lower flight ceiling than the B-17.
I knew some men who flew these planes.
Every one of them credited being alive because the B 17 could take tremendous punishment and still keep flying.
One veteran I worked many years ago was a ball turret gunner. Ernie was his name. He swore by that plane. "Bought me home very time'' he said.
IIRC, at one time during the war, we were building one B-17 PER DAY.