Revealing mistake: In the final scene where Fonda and Holbrook are looking over the carrier at the crowds on the dock you can see that only the first rows of people are dressed in period clothes, the rest of the crowd are dressed as they would have been in 1976 when the film was made.
Revealing mistake: In the aerial shot where the Pantera explodes on the highway, you can see that it's a crude mock-up on some type of rolling trailer. Also, it appears to only be moving at 30 or 40 mph, which is WAY slower than the 160 mph speed indicated in the movie.
Revealing mistake: Following their escape from the comancheros, the two wheeled wagon driven by the old woman had a set of reins coming through the slats beneath the seat indicating that the old lady held fake reins and the wagon/horses were controlled by someone inside. Later, when they left the small town and headed to her son's ranch, a little window had been cut out of the slats where the control reins came through, no doubt to improve visibility and horse control.
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)Mr Manchester
Revealing mistake: When the armed gang abduct the Mayor, a LAW rocket is fired at a Lorry, the few seconds are obviously several shots pieced together. The giveaway being the driver is a dummy as the driver has no face, even after the explosion, the faceless dummy just falls out of the cab.kazara1001
Revealing mistake: By order of the shrewd Harry Webb, the helicopter just destroyed the Cessna on the ground. The two guys decide that they are gonna walk back to civilization. Cut to the vehicle driving to the explosion site, and you can see in the desert sand ahead of the jeep fresh tire tracks from previous takes. And it keeps happening during the desert chase. (00:10:20)Sammo