Factual error: Siegfried referred to aftershave as 'cologne'. A Yorkshireman would not do this in the 1940s.
Factual error: At the end of the episode, as the veterinarians are leaving the pub, the camera pans up to the sky and you can see the full moon right next to the north star and the big dipper. In the northern hemisphere the moon is always to the south.
On a Wing and a Prayer - S4-E7
Character mistake: FO Woodham drops James in Darrowby. James gives a proper RAF salute (palm forward). Woodham responds with a US style salute (palm down).