As there was only one B-17 available, the shot of the bombers in formation was made using multiple exposures. (The same technique was used to show the Colonial Battlestar fleet at the beginning of Battlestar Galactica: Saga of a Star World (1978).)
Hewitt: [On Barker's comparing the situation to a marriage]
Let me be completly honest with you, Cryil, I've only know you for a short while, and I don't like you!
Lady Billingham: Charles, I'll make one last appeal to your better nature! We don't have to go through with this rediculos party. There's still time to cancel the Americans, and just let the nice people come! We could say there's illness in the house - some of the staff have come down with something those type of people go down with.