Isla Blair has said in interviews a huge chunk of her part was cut from the final print.
Timothy Dalton auditioned for a minor part as an RAF pilot.
Adolf Galland, the Luftwaffe pilot who fought during Battle of Britain, who later became the youngest German general at the age of 29, was hired as a technical advisor.
27 Spitfires in various degrees of repair were found for the film, 12 of which could be made airworthy. Only six Hurricanes where found, three of which were made flyable. The Messerschmitt 109 where all retired from the Spanish Air Force. The production company bought them all, about 50 of them, and put 17 of them back in flying condition. They are in the movie flown by Spanish Air Force pilots, and members of the Confederate Air Force. The 32 Heinkels, with crews, were on loan for free from the Spanish Air Force, where they still were used for transport and target towing. Two of them were eventually bought by the production company and flown together with the 17 Messerschmitts to England for further shooting. The two Junkers 52 were also on loan from the Spanish Air Force.
A B-25 Mitchell bomber, owned and piloted by Jeff Hawke and his co-pilot Duane Egli, was converted into a camera plane. Cameras were fitted into the nose, tail, dorsal and belly turrets, the nose being fitted with an optically perfect dome. The plane was painted in many bright colors so it would look different from all angles and would be easily seen by other planes. It was nicknamed the "Psychedelic Monster". Eventually flown back to USA it sat derelict for many years in New Jersey before being restored back to flying condition in Florida. Flown in air shows for many years as "Chapter XI", referring to the high cost of flying, but later repainted as "Lucky Lady".
According to the book written about the making of the movie the production crew used more ammunition (blanks of course) to film the movie - due to the fact that directors re-shoot scenes numerous times - than were actually used in the real battle.
Actor W.G. Foxley, who plays Squadron Leader Evans, was an RAF navigator whose face and hands were badly burned attempting to rescue a fellow crew member after a bomber crash in 1944. Due to his injuries he lost and eye and several fingers, as well as his other facial injuries.
American special effects creator John P. Fulton was going to do the special effects for this film. However, he died in England before principal photography began.
Cuts turned Sarah Lawson's role into a non speaking one.
During filming, the by then closed but largely intact RAF Hawkinge was refurbished to a degree, grass was tidied up, brickwork was cleaned and re-pointed. Most of the site is now a housing estate, but a few buildings and gun emplacements, some now housing a museum are still intact.
During principal photography, the real Lord Hugh Dowding, ill and confined to a wheelchair, visited the set representing his office, and met Laurence Olivier who was portraying him in this film.
Duxford Airfield, near Cambridge, agreed for one of it's hangars to be destroyed for the film. The hangar in question was considered unsafe for preservation. The other three hangars are still intact and are used as an air museum.
Houses in Peckham Rye, South London, were used as some of the blitz scenes. These houses at the time were being cleared to make way for the North Peckham and Camden Estate housing projects that were completed during the 1970s. Many of the scenes were filmed in houses while they were being demolished.
In the beginning of the movie there is a scene with a beach filled with abandoned equipment and weapons. This scene is meant to show the aftermath of the Allied retreat from Dunkirk and the French mainland.
In the real Battle of Britain, there were other German airplanes used, mainly Messerschmitt 110 fighters, Dornier 17 bombers and Junkers 88 bombers. At the time of making the film, there were no flying examples of these aircraft.
Many mock-ups of Spitfires and Hurricanes were made in the months prior to filming. Some had lawn mower engines fitted and could be taxied around the airfield, but if they braked too hard they would flip up onto their nose. This happened several times in front of the cameras and some of the footage was eventually used in the film.
Most of the extras in the scenes filmed in East London and Aldwich underground station were survivors of the Blitz. Some of the extras pulled out because the scenes were "too real" and brought back painful memories.
Over 60% of RAF Fighter Command aircraft during the Battle of Britain were Hawker Hurricanes. Due to the lack of Hurricanes in flying condition when the movie was filmed, the bulk of the air-to-air combat scenes use the more famous (and better fighter) Supermarine Spitfire. During the actual battle, whenever possible squadrons flying the Spitfire would engage the German fighters escorting bomber formations while the lower-performance (but better gun platform) Hurricanes engaged the bombers. Shooting down German bombers was the critical key since the bombers were attacking RAF airfields in the first phase of the battle and cities after the Luftwaffe changed target priorities. The film accurately depicts the British need (and desire) to destroy bombers to protect their air defense infrastructure and later protect civilian targets. For similar reasons (the lack of working aircraft of the right type) Spitfires and Hurricanes are shown flying together in tactical formations whereas in reality RAF squadrons flew one or the other type of fighter exclusively. Due to different performance characteristics, the two aircraft would not fly and fight together.
Several scenes from the German side were shot in Spain, and Spanish extras were used for portraying soldiers and ground crew.