Revealing mistake: Navarro is climbing on the outside of the train, the overhead shot shows very wide gaps between the plates welded to the windows. When the shot changes to a side-on view, the gaps are considerably smaller. This is seen several times throughout the quick scene changes. (01:47:00 - 01:49:30)
Continuity mistake: When the train take off from Nürnberg, the locomotive is on "backwards". A few seconds later is it rotated 180 degrees.
Factual error: The train consists of nine cars - six RIC cars of the Swiss Federal Railways (two 1st class with nine compartments each, two 2nd class with eleven compartments each, one 2nd class with twelve compartments, and one dining car between the classes), an MU sleeping car belonging to the CIWL (International Dining And Sleeping Car Company) between the two first class coaches, and at each end one older Swiss baggage car. The first class has 108 seats, the second class has 204 seats, and the sleeping car has 36 berths; so the train has space for 348 passengers - or 400, adding the 52 restaurant places. I wonder where they put 1,000 people on this train.
Continuity mistake: When they are attempting to lower things onto the moving train with a helicopter, it conveniently changes from overhead-powered electric to diesel. Immediately afterwards, it changes back.
Deliberate mistake: The rail line was supposedly not used in 30 to 40 years, however, in the exterior scenes approaching the bridge where the mile markers were, the tracks are well maintained, has no vegetation, and the rails are shiny, indicating a lot of train use.
Factual error: The Cassandra Crossing bridge is mentioned to be located in Poland, and you can see power lines indicating that the route is electrified. Earlier, the route is said to be closed in 1948. Polish Railways started electrifying its routes in 1960s and it is very unlikely someone would electrify that route without rebuilding the bridge (considered collapse-prone) and of course without any plans to use that route again.
Factual error: Looking into a compartment of the sleeping car, the window is placed in the middle of the outside wall. This is not the way any European sleeping car is built, especially not the MU.
Continuity mistake: When the train leaves Genève, the last two of the three second class coaches are missing.
Factual error: The model of the Viaduc de Garabit in France, the real Cassandra bridge, is really well done, but it lacks the typical French AC catenary which can be seen on the original shots.
Factual error: In most countries trains use brakes that apply automatically when a car "gets lost". The brakes are operated by air pressure and are passive brakes: they brake when the pressure is lost. Since the air comes through a pipe from the locomotive a car that is disconnected stops automatically. Emergency brakes work in a similar way: they simply open up the air-pipe, pressure drops and the train stops.
Factual error: Some of the second class scenes are obviously located in a first class saloon car. But the train has no saloon car, neither in the first nor in the second class.
Factual error: In addition to the signs on the cars, a schedule is shown within the first minutes of the film where Göttingen appears as a waypoint of the train's route. To reach Göttingen, it had either to take some unnecessarily long way from Amsterdam via Frankfurt/Main or move from Hannover down to Göttingen and the same line back to Hannover.
Factual error: The Europa-Express has a stop in Paris. I've never heard of any train just stopping in Paris, i.e. coming from one place, stopping at any Parisian station and going on to another place. Trains either start or end in Paris. Apart from this, which station is on the train's way? Coming from Basel, it should end at Gare de l'Est; leaving for Brussels means leaving Gare du Nord.
Factual error: The balance of the train seems funny: too much first class compared to the second class, the sleeping car is located among the coaches in a train which won't be separated on its way, and only one single sleeper with no slumber coaches is something incredible for a European overnight train since the 60's.
Factual error: Arrival at Nürnberg, first shot: We see the train's silhouette obviously passing the outer parts of a bigger station. Apart from the fact that Nürnberg has no typical Swiss overhead wires, it should be mentioned that Swiss electric locomotives - including the Re 4/4 II used in the movie - couldn't operate in Germany at that time (and quite few can today). This is no electrical problem, but Swiss pantographs are too narrow for the wide German catenary zig-zag, they would glide off and tear down the wire.