At the beginning of the film, when the dirigible is landing at Lakehurst, New Jersey, the starboard engine is not running. After landing and mooring, Ned gets off the ship and the starboard engine is running.
When Ned Trumpet is instructing his men on the flight line, an airship is seen in profile behind them. When he dismisses them, the airship has turned away and is seen from behind. As soon as a closeup is seen, the airship is back in it's original position in profile.
When Trumpet is talking to Tim Shannon beside the airship near the beginning, his moving shadow is visible on the rear-projection screen behind him.