Wooo!
I'm a bit of a war film buff myself (especially aviation-related ones), so damn sure I'm looking forward to this! It might be a bit "Hollywood", but it's rare for a WW1 film to be made these days, especially one about the flying side of it. Entertaining, it certainly seems to be!
Yes, the Memphis Belle is a real aircraft - it still exists, and is under restoration at the moment (although there is one flyable B-17 (a later G-model - the 'Belle was an F) painted up as the Memphis Belle) for the National Museum of the United States Air Force near Dayton, Ohio.
Here's the real thing:
And the one that flies in the 'Belle's markings (owned by David Tallichet):