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.
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.
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".
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 That particular model had already been withdrawn from service over a year before the movie takes place. (E.III was withdrawn early 1916, the movie takes place late 1917).
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.