Revealing mistake: In the scene where Lorraine Bracco points a revolver at Ray Liotta's head, after Ray Liotta turns the tables and now points the gun at Lorraine Bracco as he gets up and walks away you can see Ray Liotta steps on Lorraine Bracco's hand and she opens her mouth wide like shes screaming but it must have been cut from the audio, as Ray walks off camera his expression changes to show that he knew he had accidentally stepped on his co-workers hand.
Revealing mistake: Early in the film, when Hughes and another guy are walking past one of the replica WW1 aircraft used for the "Hell's Angel" scenes, you can see the ends of the cylinders of the modern air cooled engines they used to power it. The original aircraft (SE-5A) used a water cooled V8 which wouldn't have been visible.
Revealing mistake: When Mary of Guise is found dead by her nephew, he lies her down and puts his head on her chest. As he comes down, her eyes slap shut! If she were dead, they would remain open.
Revealing mistake: In an early scene Cole and his future wife watch fireworks over Paris through a doorway overlooking a balcony. The explosions are reflected on the glass of the open door, which is at an angle to the POV. But the CGI fireworks and their reflection in the glass are squashed to fit into the foreshortened pane of glass. In reality the reflected image would be like any mirror, with the image inverted left-for-right.
Revealing mistake: Have a look at some of the beards (and wigs) in this movie, the facial hair is coming loose on several of the disciples' beards.