Sinclair informs Croft that Gresham uses a Nieuport "that he swears by", but every time we see Gresham aloft he is flying an SE5 like the rest of the squadron.
Croft and Sinclair fly an Avro 504 on a reconnaissance mission. They are attacked by a German fighter. When we see the Avro from the German pilots point of view, it has transformed into a Caudron Luciole, because those scenes are outtakes from "The Blue Max".
Christopher Plummer was 46 years old when he filmed this. Even if his character had was intended to be ten years younger than the actor playing him he was still far too old to have been allowed to fly on a mission by the Royal Flying Corps (who had an unofficial cut-off age of 30 but in reality their flyers tended to be in their early 20s).
In the first air combat scene, the German aircraft shown is a Fokker E.III monoplane. That particular model had already been withdrawn from service over a year before the movie takes place. (E.III was withdrawn early 1916, the movie takes place late 1917).
Major Gressham is depicted as the leader of 76 Squadron, Royal Flying Corps.
That particular squadron was based in England throughout the war and never saw action in France or elsewhere.
In the end credits they have listed one of the officers as Brigadier Whale. The British Army did not have the rank of Brigadier until 1928 which is a crown and 3 pips on the shoulder. The rank was in fact Brigadier-General which is a sword and baton This rank was in use in the British army until 1921. The uniform was historically correct just the listing at the end was wrong.
When visiting the bordello, one of the companions remarks to Crawford that Croft is 'tout seul' ('all alone'), but instead of the glottal stop, she carries the 't' into the second word, effectively saying 'toute seule' (feminine)-this is typical of Anglophone efforts to speak French. She should have said 'tou- seul', omitting the 't' completely.
Because of the use of disguised, more modern, inauthentic aircraft, most (with the exception of the mocked-up SE5s with their forward-facing radiators hiding the V8) are shown with radial, instead of, rotary engines, where the engine block rotates around a fixed crankshaft.
When telling Croft about the biscuits available in the officers' mess, Bennet claims that he used to have Bourbons until they 'got nicked'. This popular chocolate-flavored biscuit was introduced in 1910 but was originally called the 'Creola', re-named as the Bourbon in the 1930's.
In the scene where the squadron are assembled in the mess to entertain their german prisoner, one of the British pilots is wearing a football style scarf. common in the mid 1970's when the film was made.
Because of the use of more modern 'disguised' aircraft, most of the kites shown have pneumatic tyres on their undercarriage, instead of the solid rubber tyres correct to the period.
Upon arrival at 76 squadron, Croft introduces himself to Bennett (the mess Cpl) as "Second Lieutenant Croft". At this point, the RFC were still technically part of the Army. Tradition and custom dictate that he and other officers refer to his rank as simply 'Lieutenant'. The 'second' would only be mentioned in official communiqués.