In one patrol in my U-670, I got back to base with ~40% hull integrity due to 3 (!) successful air attacks on my boat. This was in 1944. I didn't get very far out of Biscay before turning back because my men did not spot any planes even with both periscopes up along with the snorkel. I aborted mission due to heavy damages. The area outside Biscay is hell in comparison to Biscay itself, for some reason. Quite odd, I only found one plane in Biscay, but I found about 20 just outside.
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