Factual error: When first introduced to the Poles' training flight and they break stating "repeat please", the front 2 aircraft are Hurricanes but the 3 remaining aircraft are the stand in 109's. If you look closely you can see the rear wing struts to the fuselage.
Character mistake: Many windows only have 1 or 2 panes taped over to prevent glass from shattering when it's hit. Unless every pane is taped over this will achieve next to nothing.
Revealing mistake: In the opening scene when the Hurricanes take off from the makeshift airstrip in France, well established earth-banked aircraft pens can be seen in the background. This indicates that the Hurricanes took off from a well established military airfield.
Continuity mistake: When the Senior Civil Servant is reading Dowding's letter there is a knock at his door. In the next frame the Civil Servant has removed his glasses, appears more leaned back in his chair, and the position of the letter/page has also changed. (00:06:00)
