Factual error: In the car at the beginning of the movie, Jean uses her telekinetic powers to switch the radio from a station playing "By the time I get to Phoenix" by Glen Campbell to Warren Zevon's "Werewolves of London." It's 1975, and Zevon recorded the song only in 1978 (although the song itself had already been written in 1975, other artists played it in live concerts in the Fall of that year). (00:01:30)
Factual error: The space shuttle is spinning due to a stuck thruster. In such a case, the spin would be continually increasing as there is no air resistance. The X-Men shoot out of the thruster and the spin stops. Not factual. They would have needed opposite thrusters to stop it. (00:11:55)
Continuity mistake: After the "standard medical", Hank takes the heart rate monitor off Jean's left wrist and hand asking her how does she feel. She responds "I feel...good", hand raised, and in the next shot she has again the left hand resting on her tummy. (00:20:35)
Continuity mistake: In the shot just before the moment when Jean tells Scott "I'll always come back to you", she is shown lowering her hand, which has the thumb under the earlobe. When she does say the sentence, her hand is back up and with the thumb all the way in front of Scott's ear in a very jerky, easy to spot, lack of continuity. (00:21:40)
Continuity mistake: During the nice big dinner at the house that is going to be taken over by the aliens, the future leader, Margaret, tells her husband she's gonna go check on the dog. The man to her right holds the bottle of wine and gives it a big thumb up as he peruses it. In the reverse shot, he's pouring wine from that bottle with the former thumbs up hand, and back to the original view he's still in the same pose of approval as before, bottle switching hand again. Similar mistake happens when she, now assimilated, comes back: check out of the glasses in the hand of the guys at the table. (00:22:20 - 00:23:45)
Continuity mistake: Despite having the Phoenix power at the end of X-Men: Apocalypse, which manifests around her as a Phoenix firebird and she uses to defeat the titular villain, Jean Grey doesn't actually get merged with the entity until 9 years later in this movie.
Suggested correction: Jean used her full psychic powers in the previous film, not the Phoenix Force. Even without the Phoenix Force she was an incredibly powerful, Omega Level mutant.
The Phoenix firebird is literally shown to be emerging from Jean's body when she kills Apocalypse. She can't both have the Phoenix firebird already within her and then somehow also have it invade her body in this film. The mistake is valid, and I would argue it should be listed as a plot hole more than a continuity error.
Plot hole: There are two timelines in the X-Men franchise - the original films and the prequels, up until Days of Future past, which alters the future, and at the end reveals that Jean Grey, Professor X and Cyclops are all alive, rather than dying as they did in X-Men 3. The "new" timeline is then followed in Apocalypse and this movie, giving them a bit of leeway to make changes, much like the new Star Trek movies. Only problem is...Jean Grey dies in this movie! So no way her older self can be around in DoFP.
Suggested correction: I think you might have missed the final shot in the movie, when the camera pans up from Charles and Erik playing chess and the Phoenix firebird is shown flying across the sky/stratosphere, implying that, much like the Phoenix's legendary namesake, Jean had risen from the ashes so to speak. There is precedent for this in the comics, plus there were supposed to be more X-Men movies after this one until the Disney/Fox merger happened.
Yes, but she even said she evolved beyond earth, so that is basically saying that she died. Or she isn't on earth anymore.
Suggested correction: Bryan Singer confirmed that the end of Days of Future Past with Jean Grey being alive is one of many timelines, there are more than 2 timelines in this universe, meaning that despite all the X-Men being alive in the future at the of Days of Future Past, they can still all die in other movies like in Logan and Dark Phoenix.
Other mistake: Despite taking place roughly 30 years after "X-Men: First Class," Xavier and Magneto have hardly even aged. Both would have been in their late 20's at the youngest in "First Class" and in this film neither looks any older than 40. It's not because of their mutant powers either - only Wolverine and Mystique were specifically mentioned as having a slower rate of aging because of their powers.
Plot hole: The shapeshifting aliens without even flinching take full barrages of M4A1 carbines point blank, absorbing in full all the damage, but somehow they can be kicked and punched and get hurt and stopped by scraps of metal, knives, whips, Beast clawing at them, and even better, the non-superpowered Nightcrawler snaps the neck of one of them.
Suggested correction: None of them are killed or actually harmed by any of the attacks as later shown when they just get up again. They have stolen human bodies and those bodies still react like a real human body does, they just take some time to regenerate.
Without mentioning the D'baris from the comics who don't steal bodies but just pose as humans, in this movie they are shown having their own body to begin with, with an ability to assimilate humans with their memories and appearances: it's doubtful they'd have a spine to snap. Their reactions are just all over the place though: they take virtually no time to regenerate full barrages of automatic weapons, staying all the time on their feet not even flinching and showing no pain (also, being equipped with superhuman strength, since they toss people all the way from one end of the train wagon to the other with one hand). They show no reaction to bullets maiming them, but if it's a main character taking a swing, then it's a hit - even if non lethal. The main villain reacts to no bullets but when Nightcrawler was cutting her up she swayed wildly under his every strike, just as an example. I get it that it's choreographic, but it just makes no sense.
The turret shot bullets through them and they quickly healed.
Continuity mistake: After Jean kills Raven, she does not have any blood on her before she flies away. She is then shown in the rain trying to wipe away a large blood stain from her shirt in the rain.
