When ACM Dowding and the Air Minister are discussing relative aircraft numbers, the minister states, "We have radar". The term radar was not used in Britain in 1940. The term RDF was used.
The term radar was invented by the US Navy in 1940 and held as secret until later in the war.
In one scene where the fighters scramble from Hawkinge, you see them lift off and fly over Folkestone in the distance. In this shot you can see the large tower block which is the Civic Centre, it wasn't built until long after the war.
All of the flying models of the Bf-109 were the version built under license to Spain with the upright Hispano-Suiza engine. It has the overhead cam covers on top of the cowling which would obscure some forward vision compared to the smooth-top cowling of the inverted array having the overhead cam mechanism on the lower portion. There were few flying versions of the original Bf-109s, likely too few to be deemed usable for the film at the time.
Set in 1940, the German army's convoy in Nazi-occupied France
contains at least three Mack B-Series trucks, which were only built from 1952 to 1966. The Germans are also shown riding in US half-tracks.
As the Heinkels are flying up the Thames for the first daylight raid on London, the lead bombardier clearly says "Five seconds" in English, although the audio track has him saying "Fünf Sekunden" in German.
On "Eagle Day" the Germans begin their bombing raids and Air Vice Marshal Park orders the squadrons to scramble. The clock in the command center doesn't change, even though Park admits that several of the squadrons took "six or seven minutes," to scramble.
During the dogfight sequence when Canfield is shot down by German fighters, the shot of his aircraft exploding in mid air as it is heading for the ground is not a Spitfire, but Canfield flies a Spitfire during the film and during this all important scene. He is seen taking off in one immediately prior to this sequence.
Harry Andrews' character is seen seated at his desk, wearing glasses, reading Dowding's letter to Churchill. As Dowding enters the room Andrews turns to speak to him and his glasses are now absent. The timing of the scene precludes him removing them as part of the action.
In the prologue set in France, when the first Hurricane taxis to a halt and the pilot gets out, the head of someone else in the plane is visible. It was probably the "driver" of the plane - several models constructed for the film which were capable of taxiing only.
At about 33mins in there is a German pilot briefing using a map of Southern England. The officer points out the targets, Dover, Manston.... Hawkinge. When he points to Hawkinge, he is really pointing at Hastings, which is about 40miles to the West.
At 26m 18s, a burning Heinkel is descending over Admiralty Arch in a north-easterly direction, precisely away from Buckingham Palace, which is about a half a mile to the south-east. A couple of seconds later, it continues its descent straight over Buckingham Palace.
(at about 33 minutes) The briefing to German airmen also incorrectly mentions Manston (Thames estuary) when the officer actually is pointing at the map roughly near Worthing - about 150km away on the south coast.
At the end of the movie a list showing all of the non-UK pilots flying for the RAF is shown. At the end of the list they mention one Israeli pilot flying for the RAF. Israel was not created until 1948, and in fact the pilot in question was from British Mandated Palestine. The one Icelandic pilot flying for the RAF in the Battle of Britain is not mentioned, neither are the pilot from Egypt, one from Austria nor the two from Jamaica.
The film indicates the Blitz happened because the RAF bombed Berlin after a German bomber accidentally bombed a civilian area of London. However, in reality Hitler ordered the Blitz because the RAF had already bombed German cities every night since 15th May 1940.
When Air Vice Marshal Park visits Canfield at the latter's airfield, the designation of the squadron, "188", is shown on the door to the main office. No. 188 Squadron RAF did not exist during World War 2. No. 188 Squadron RAF was a World War 1 squadron that was active between 1917-1919. It has never been re-activated.
The first German-language scenes show the Luftwaffe's inspector-general (Field Marshal Milch) making an inspection of several bases in occupied France. Despite his rank as a field marshal (as evidenced by the marshal's baton he carries), he is only addressed as "general," and the rank insignia on his shoulder boards appear to show the three pips appropriate to a full general (Generaloberst), rather than the crossed batons that would be correct for his actual rank.
In the attack from Norway, when the lead aircraft is attacked head on, it's clear that the camera viewpoint - supposedly that of the German pilot being attacked - is turning with the fighters as the Spitfires are maintaining a steady distance and the background sky is moving, rather than closing fast with a steady background as would be the case with a real head-on attack.
During the attack from Norway by Heinkels of Luftflotte 5 (at around 1 min), the Lieutenant flying the lead plane says over the radio "Tomato Eins an Alle, Tomato Eins an Alle, noch zehn minuten bis Ziel". In some versions of the film on the subtitles the first part of this is translated as "Tomato Heinz to all". The correct translation is "Tomato One to all, Tomato One to all, still 10 minutes until target".
When a shot-down Heinkel bomber is plummeting straight down in vertical position, a brief interior shot shows the crew struggling to climb up to the escape hatch. In a free falling vehicle there are conditions of zero gravity inside it (as in a falling elevator) so crew would actually have no trouble at all to float up to the hatch.
When the Germans first start the daylight bombings of London, a group of boys is seen playing in the river. As the German bombers approach, two boys start to argue about the type of aircraft approaching. One boy says "Messerschmitt" and the other says "Heinkel". However, the subtitles translate it as "Iron Cross".
The cast credits are stated to be in alphabetical order and are actually presented in three groups in alphabetical order within each group, but in the second group the name John Baskcomb is mis-alphabetized, and so is Alf Jungermann in the third group.
The subtitles on the screen incorrectly translate a German fighter pilot as saying, "Indiana break left." What he actually says is "Indians, break left," Indians being common Luftwaffe fighter code for enemy aircraft.
When Hitler is giving the speech about the bombing of London in retaliation of that of Berlin, he is incorrectly translated. He talks about 'kilograms' of bombs being dropped, the translation gives only 'number of bombs' and not the correct number at that.
In the scene where Kenneth More is talking to Susannah York
and the Germans start to bomb the airfield; the blast from the first bomb landing in the distance is heard at the same time as the blast occurs. Both actors react to the true sound seconds later, making them look rather slow on the uptake.
English subtitles show a complete lack of understanding of the RAF in the war. Stanmore is repeatedly shown as 'Danmoor'. Biggin (Hill) is shown as 'Big Wing' and 'Begin', Hornchurch is completely missed off. Ventnor is misspelled, 'break left' is shown as 'brave left', 'lazy shower' as 'lazy shover' and so it goes on.
Sgt Pilot Andy never pays the taxi driver who brings him to the London docklands. As the driver only explains that the route is blacked after he has stepped out, he could not have paid the correct fare inside the cab.
A Spitfire gets bombed during a take off run and crashes into a truck which explodes. The stuntman who runs away from the truck can clearly be seen waiting for his cue to start running. Audible aircraft tire squealing is heard on a grass field. The truck also explodes just before the Spitfire actually hits it.
During scenes shot in the British cockpits it becomes obvious that many of the British aircraft have been painted on the inside of the cockpit canopies. All the real aircraft are seen to gently rise and drop through out the scene, but the aircraft painted on the canopies stay put in their positions. Sometimes a distant aircraft will partially overlay the closer real aircraft.
(at around 30 mins) A Polish flight of Hurricanes is flying in formation with Messerschmitt 109s (the 109s at the rear). The 109s can be easily distinguished from the Hurricanes by their tailplane struts.
The front gunner of a German bomber is hit by machine-gun fire and thrown backwards by the impact, revealing large amounts of fake blood already visible on his stomach and abdomen. Blood would take at least a few seconds to leak through heavy flight clothing.
As the Heinkels approach the London Docklands, the shot from behind the aircraft shows them not moving in relation to each other at all, yet the background aerial view judders about, revealing that this is a group of plastic models being filmed.