This is the B-17 F, the model that Andrews flew in combat.

The E, F and G models of the B-17 all had big dorsal tail fins that provided space for a tail-gunner to sit beneath the rudder to operate two 50-caliber machine guns.  They also had top and bottom gun turrets, each equipped with two 50-caliber machine guns.

The later B-17 F, and all B-17 G models, would be also equipped with an underslung, twin-gun chin turret in the nose of the plane.