Sir Michael Caine initially thought he was too young to play a squadron leader. However, veterans of the battle told him he was actually too old for the part.
Many of the actors were too old to play pilots. In reality, the average age of a pilot during the Battle of Britain was only twenty.
The large number of aircraft collected for this movie made it the thirty-fifth largest air force in the world.
Sir Michael Caine tells in his biography that there were severe arguments with the German former Luftwaffe pilot Adolf Galland, who served as a Technical Advisor for this movie. Galland maintained that Luftwaffe did not really lose the Battle of Britain. He further argued the battle was irrelevant as Adolf Hitler never intended to invade the UK. Galland shared Field Marshal Gerd von Rundstedt's view that Operation Sea Lion was a deliberate bluff to put pressure on the UK to accept Hitler's peace offers while the Axis prepared for Operation Barbarossa.
Adolf Galland, the Luftwaffe pilot who fought during Battle of Britain, who later became the youngest German General at the age of twenty-nine, was hired as a Technical Advisor.