A mistake, chaps! Watched this because the trailer seemed OK.
I, too, gave up before halfway. Saluting indoors without hats? Officers saluting sergeants. Too much saluting altogether, in fact. And using each other's messes! Why do the inaccuracies matter? Well because they completely destroy the authenticity of the drama. It may be possible for someone with no connection to the RAF to enjoy the screenplay but if you want to be involved in a film, you have to believe in the characters. And with 32 years service in the RAF, I found these characters absurd.
Watch the Dam Busters to see how people really behaved. The effects might be crude, but the way people spoke and behaved is spot on. Because most of the actors had just been demobbed themselves.
Skip it.