They hold a huge dance in the hangar at night, and Dennis leaves to walk to the Memphis Belle through the hangar doors, which are wide open. The whole flight line, tarmac and hangar are bathed with light - on a US Air Force base in East Anglia during the height of the German bombing offensive. Haven't they heard of the blackout? Why not just paint a big fluorescent sign on the runway saying 'Please Drop Bombs Here'?
Very few flyable examples of the B-17 existed at the time of the shooting of the movie. One airplane "stood in" for several by having its decals changed. The B-17G featured in the film has since undergone a meticulous restoration and now lives in Renton, Washington, USA. Though it is fully flyable, certain certification issues with the Federal Aviation Administration have kept it grounded.