Factual error: Parts of the scene where the brightly lit alien mothership passes directly over Devil's Tower are shot with the camera looking almost directly up, as would be the view from the people below. In these scenes, Devil's Tower remains totally dark despite having this huge light source directly above. The mothership is so huge that a shadow cannot explain this darkness.
Continuity mistake: While Roy watches Barry make the mud mountain, its top is flat, but a frame later it's taller and peaked.
Other mistake: When Richard Dreyfus rushes to the street to grab the trash can as the trash truck is coming down the street, his family is the only one on the block that has their trash cans out. It's obviously trash day and many of the houses are yet to be serviced by the approaching trash truck. (01:14:30)
Continuity mistake: After Roy makes a mountain with the mashed potato, the bowl has food coming out. Two seconds later, after Roy talks to his family, the food is gone, despite no one having touched the bowl.
Continuity mistake: Roy is stalled in his truck at the railroad track. We see the mailboxes behind him burst open and all the mail comes flying out. Next shot, from inside the truck, the mailboxes are closed. Then another outside view shows them open again.
Factual error: Roy has the TV on during the creation of the Devil's Tower model. The show Days of Our Lives is on. When it cuts away, a Budweiser commercial comes on. Beer commercials are never on during daytime weekday soap operas. Then the news comes on and it's ABC news. Days of Our Lives is on NBC and always has been.
Continuity mistake: In the alien departure scene at the very end of the film, a solitary alien exits the mothership and approaches Francois Truffaut, who extends his right hand directly towards the alien and makes the Five Tones hand gesture. The camera cuts to another angle half-way through the gesture, and we see that Truffaut is now looking sharply to his right, over his extended arm, and smiling broadly at the alien as he completes the hand gesture. Apparently, Truffaut's body and extended arm pivoted 90° away from the alien mid-way through the 2-second gesture.
Revealing mistake: When the gigantic mother ship appears and sweeps over the rendezvous base at Devil's Tower, the camera cuts to look straight up at the advancing craft as it blocks out the starry night sky. Watch carefully to see some stars passing right through the leading edge of the mother ship, revealing a flaw in the traveling matte effect.
Continuity mistake: While Roy and a crowd are gathering on the side of the road waiting for the aliens, a group of old men play cards on a table packed with food and drinks. When the angle changes (when Jillian meets Roy) one of the men has vanished and the table is empty.
Continuity mistake: In Sonora, a man introduces himself as a cartographer and walks 5 meters away from a crowd. When the angle changes he's barely half a meter away from the crowd.
Continuity mistake: While being blinded by the UFO, Roy grabs his flashlight from the round part next to the ligh bulb. Half a second later he is grabbing it from several centimeters below.
Revealing mistake: The huge UFO opens its door and a brilliant light comes out, but from the opposite angle, the reflection on the people's glasses is a black landscape and a tiny spot of light.
Continuity mistake: During the meeting between people and the Government the stuff on the table keeps moving between shots: the bowls that the guy slides trough the table, the tray with a glass bottle, and the book in front of Roy.
Continuity mistake: When Roy wakes up his wife to tell her about the UFOs, the pink tissue paper in the box behind swaps from lying flat to standing up between shots.
Continuity mistake: In Sonora, the scientist walks towards some Mexican officers standing by a stone wall, and a wooden fence is ahead. A frame later, they're standing next to an iron spring and a wicker basket that have appeared out of nowhere.
Plot hole: The aliens provide coordinates for a place to make a rendezvous with humans but do not specify a time. It's possible they're monitoring and will arrive when they see enough humans gathering at Devil's Tower, but the humans seem to expect the aliens to come more or less exactly when they actually do, somehow.
Suggested correction: Scientists were prepared for the aliens and knew when and where they would arrive, as seen by the extensive complex built at Devil's Tower. However, as Claude Lacombe, the French scientist, speculates towards the end, hundreds of humans may have had the Devil's Tower image recently implanted in their minds, saying they were "invited" but never made the connection. Neery figured it out and was compelled to go there at that time. Neery was then allowed to join a group of trained volunteers that were already prepared to go on the ship, while the previous "abductees" were being returned to Earth.
The aliens had not given a time to meet. The scientists may be taking it on faith that the aliens will know that they've arrived at Devil's Tower and are ready, but the way the subject of timing is left unaddressed on screen feels like an oversight.
We don't know for certain if the scientists were given a specific time, but it appears they were, or at least a general window. The long-lost objects, like the ship and the military aircraft, suddenly showing up in the desert, is an indication the process has started. If humans were given the precise location where the alien ship would arrive (Devil's Tower), then, logically, the aliens would also communicate when. The scientists were communicating with the aliens using tonal sounds. Early on, the scientists received map coordinates through dish satellites as repeating pulses. They would likely receive time information the same way. As often happens in movies, this info may be something that got edited out of the film, causing an inconsistency.
This might be one of those edge cases. Under most circumstances I'd agree we could assume arrangements were made off-screen by virtue of the fact that the rendezvous occurs successfully in the first place; but in the context of this movie, in which any and all forms of contact with the aliens is treated as profound and significant, leaving it unaddressed (not even with a line of dialogue) comes off like a plot hole. I suppose we'll just have to let our fellow website readers decide.
Continuity mistake: When Roy first encounters the alien ship at the railroad crossing, when the bright light comes on, he leans out of the truck window, and the right side of his face is exposed to the light. Therefore, it is the right side of his face that should have been burned. Subsequent shots show that the left side of his face is burned. (00:21:00)
Suggested correction: Roy shields the right side of his face with the hand holding the torch so that it's not exposed. His left side is not covered so it gets burnt.
How could the left side of his face get burned, if it's not exposed to the light?.
Continuity mistake: Roy meets Jillian and then walks away to look after Barry. In the next shots with the kid, Roy's hair is longer and messed up.
Continuity mistake: When Ray first arrives at Devil's Tower and stops the station wagon, the broken fence post resting on the hood changes positions between shots. In the view of him through the wind shield, the post is lying straight, parallel to the length of the wagon. In the next shot, it is suddenly at an angle, even though the car hasn't moved. (01:21:30)
Audio problem: In the scene just as Roy, Gillian, and Larry take off for Devil's Tower, the army officer is on his car phone speaking to his superior. When his superior tells him if they don't get Roy and company off the mountain in one hour, to use EZ4. Lacombe, who was talking to David at the time, looks at the officer and says, "What's EZ4?". Lacombe should not have known what was said over the phone, as only the officer and we, the audience, knew what was being said. It wasn't a speaker-phone. [The army officer was using a VRC(vehicle radio console.) Not a cellular phone. The radio has a speaker mounted on the front of the console in addition to the speaker in the handset. So everyone would be able to hear the conversation on the radio. ].
