In the film Leslie Howard's Mitchell says he wants his new fighter to be "a bird that breathes fire and spits out death and destruction--a 'spitfire' bird", giving the aircraft its name. In reality, when 'R.J. Mitchell' was told the name the RAF had given to his design, he is supposed to have said, "That's the sort of bloody silly name they *would* choose!"
Several real-life Battle of Britain RAF pilots such as Anthony C. Bartley and Brian Kingcome are featured in small roles in the opening and closing sequences at the dispersal hut, talking with David Niven's character and discussing their "kills".
In the opening scenes, the RAF pilots who are being briefed are from No. 501 Squadron. The Spitfires are carrying the markings "SD", which were carried by No. 501 "Mandrel" Squadron. At the height of the battle these pilots would have been flying the Hawker Hurricane instead of the Spitfire. The squadron had fought in the Battle or France before the evacuation of the BEF at Dunkirk at the end of May 1940. The squadron then moved to RAF Kenley, from where they fought the Battle of Britain.
The film's opening prologue is a quote from Alexander de Seversky. It states: "In the grim days of 1940, when Britain stood alone between mankind and the Nazi hordes, a fighter plane staved off disaster. Behind this plane lies the heroic and unselfish story of RJ Mitchell, the British engineer whose story is a great inspiration to American engineers and designers--those invisible members of the air-power team--who toil relentlessly to forge superiors weapons, so that their teammates, the gallant air-men, may go into combat with the kind of advantage they deserve."
The music heard while the Nazi leaders are shown on screen, with an English voiceover explaining what they are saying, is a pastiche of themes from Richard Wagner's four-opera cycle "The Ring of the Nibelung." This use of Wagner's music reflects Adolf Hitler's admiration for Wagner both as an artist and a fellow anti-Semite.
The Spitfire first flew for real on 5th March 1936 and was flown by Vickers Supermarine's chief test pilot 'Mutt' Summers. Summers also flew some of the early test flights for the bouncing bomb used during the Dams Raid in 1943 which is portrayed in The Dambusters (1955).
Sequences of the Supermarine S4 in 1925 employ most of the only known footage of the actual plane on its first take-off and in flight. The inferior quality of the film is disguised by presenting it as seen through binoculars.
Lucy, Lady Houston, did indeed travel around the British Isles with an electric sign on her yacht "Liberty" in 1932. However, instead of "DOWN WITH THE GOVERNMENT. WAKE UP ENGLAND" as shown in the film, it displayed a rather more blunt "DOWN WITH MACDONALD THE TRAITOR", in reference to the then Prime Minister.