B-17 WWII Planes

A few weeks ago we went to see some old planes used during WWII in Salt Lake. Chris's Grandpa actually flew in a B-17 in WWII he was the ball gunner (I think that's what it's called) its this tiny little ball pit on the bottom of the plane. He was shot down and was a prisoner of war and only him and one other guy in his crew survived. I don't remember all the details and I feel like Chris would be a lot more qualified to share his Grandpa's story.