The Eighth Air Force flying B-17s out of England had a loss rate of about 5% PER MISSION. Not all those people died, some became POWs, but either way your chance of coming back to base on average was 95%. Now multiply that by a 25 mission tour and that comes out to be (0.95)^25 or roughly 28% of getting through without dying or becoming a POW. Not surprising they were a little crazy. It was likely a job requirement.