Factual error: After Devereaux is shot, he sees an oncoming locomotive on the opposite track coming towards him. The Streak is traveling over sixty miles an hour on its track, but in the background to the left of the oncoming locomotive, the Streak's tracks and background are stationary. Since the Streak is traveling at high speed, the forward tracks and background would not be stationary, but rushing towards Devereaux's point of view, along with the oncoming locomotive.
Visible crew/equipment: While Devereau is burning the Rembrandt Letters, in the background view out of the train window, camera equipment and crew can be seen in the reflection in the windows of the buildings. Also, in the same scene, some people are standing, posed very unnaturally in front of the windows, blocking only some of the reflections. (01:29:20)
Continuity mistake: In the washroom scene, in between Gene Wilder saying "That's humorous" and "May I speak", Richard Prior is applying the shoe polish on Gene Wilder's forehead and not the nose, but next shot facing Wilder, there is no polish on Wilder's forehead but there is polish on his nose. (01:14:25)
Continuity mistake: When Devereaux is shot by the cop in the helicopter, he's alone in the Silver Streak's engine compartment, leaning out the open door. He's then hit by an oncoming engine. In later shots of the runaway train, there's no sign of his body or of any blood, and the door has somehow closed itself. (01:44:00)
Factual error: When they uncouple the cars the back of the train comes to a stop, but the front should have also. When they uncouple the cars, we see steam or smoke come out of the brake hose, brake hoses use air. At the speed that the train is going it probably would have derailed in the yard long before it hit the end, yards have tight curves and are made for slow speeds. I don't care how fast the train is going, it would not have caused that much damage.
Factual error: You can't climb up on top of passenger train cars like they did. Handrails were welded on outside of car for the movie shoot. Also the red marker lights on the front of the diesel loco as it crashes through the wall are tail lights that should be on the rear. No lights would be lit for a regularly scheduled train.
Continuity mistake: In the train crash sequence, the real locomotive's headlamp has two lights side by side. However, when the movie cuts to the model crashing into the terminal, the headlamp has a single light. The model also lacks grilles on either lower face which were present on the real locomotive. (01:48:00)