Continuity: In one shot the phone receiver gets knocked off the hook, but moments later the phone rings and the receiver is in place on the phone.
Revealing mistakes: Just prior to the first murder-scenario fantasy, Sir Alfred's shadow is visible on the rear-screen projection screen as the camera tracks in on his eye.
Continuity: During the rehearsal scene. A cigarette pack disappears from the podium as Harrison conducts.
Errors made by characters (possibly deliberate errors by the filmmakers): "Antigonish", a town in Nova Scotia, is mispronounced by an airline official at the beginning of the film.