I've been re-reading my copy of Ernest Gann's book of that name (not to be confused with the movie). It is hair-raising to read about commercial flying in the late 1930's and 1940. DC-2 and DC-3 airplanes flying routes at no higher than 5,000 feet. Far fewer navigation aides and poorer weather info than we have today, yet they were flying to schedules regardless of the weather. Tragically, many of Gann's contemporaries were killed during those years and in the War years flying cargo. The first pages of the book are lists of "silent wings" flyers that were his friends.