Oh my, the real life history of a Uboat crew, especially from '43 on...
- it was like 3 of every 4 died, with airplanes contributing significantly. Check-out
U-Boat Fates, and others of that ilk. Possibly the only country with a higher mortality rate might have been the Japanese submariners... While 12 planes might be about 6 times more than a patrol, it wouldn't be unheard of. Planes are to be avoided...