My husband recently read the book that told about the espionage activities during WWII - I think the title is "A Man Called Intrepid" - and the author said that they knew ahead of time that Leslie Howard's plane was going to be shot down but couldn't do anything about it because it would have destroyed an important source of information behind enemy lines. He was talking about some of the very painful and difficult decisions that had to be made at times.
Raymond Burr's first wife was purportedly on the same plane as Leslie Howard when it was shot down by Ju-88s while leaving Portugal.
Burr's wartime service is probably the most little known of all the Hollywood icons; he had to have numerous surgeries related to his wartime injuries (US Navy, Okinawa) during the making of the Perry Mason series, where he was either shown laid up "sick" in bed, or replaced by a guest attorney (like Bette Davis).