Continuity mistake: Many times through out the film the red bag that contains all the money is not seen with the main group, even though they supposedly keep it with them at all times. The most noticeable example is when the two main characters first fly into Spain in the balloon and when the interior of the basket is visible the bag has simply vanished, but they have it again later.
Continuity mistake: When Luz is talking to Jet on the phone for the first time, from the front she's fiddling with the phone cord with her left hand. When it cuts to the reverse, however, her hand is flat on the desk.
Continuity mistake: The opening scene states the date as April 10th 1865, the day of the train station robbery. Siringo tells Vance at the school money-raising event that the robbery took place 8 weeks ago, but when Clint is buried at the end, his death is April 25th 1865, only 2 weeks after the robbery.