The casualty rates for bomber operations out of England against Nazi Germany were very high, but I'm pretty sure that 75% of the men who started a combat tour weren't killed. Casualties include wounded, captured, and missing in addition to deaths. Many were shot down and captured (tens of thousands of them) and tens of thousands were killed. Many shot up planes returned to base with wounded or dead crew members on board. A very low percentage managed to evade capture and make their way back to friendly territory.

There were some missions, especially in 1943, where the loss rate was far above 5%. Two missions in particular, some 60 out of 360 planes were lost. Each plane carried a crew of 9 or 10 men, so we're talking about losses of over 600 men (counting the dead and wounded that were on planes that did return) on 2 days alone.

Here's a list of 8th Air Force losses in WWII. Look at those totals:


Aircraft/ Number / Crew
Type / Lost / Size
B-17 / 4,754 / 9 or 10
B-24 / 2,112 / 9 or 10
P-47 / 1,043 / 1
P-38 / 451 / 1
P-51 / 2,201 / 1
Total 10,561

RAF losses were very high, too. There were nights when dozens of bombers were lost in action over Germany.

A friend of mine was a B-17 pilot in the 91st Bomb Group in 1944. He'd made it through his 25 missions almost without a scratch (to his body, not his plane), so he decided to do another tour*. He was a combat check pilot, so he took new crews for their first mission over enemy territory. He was shot down on his 28th mission. The other 8 men were on their first mission. Everyone managed to get out of the plane alive, but one was machine gunned while in his parachute. Seven of the remaining 8 were captured by the Gestapo and ended up in Buchenwald, a fate that only about 80 American and another 80 or so Allied airmen had to endure, as chronicled here.

*He now says that was the dumbest decision of his life, but he was only 19 at the time.