This film, The New Mutants (2019), and Deadpool 2 (2018) were filmed around the same time with New Mutants filmed in Boston, Massachusetts, United States, Deadpool 2 in Vancouver, British Columbia, Canada, and X-Men: Dark Phoenix in Montreal, Quebec, Canada.
This will be the first X-Men film to not feature or reference either Logan/Wolverine of the actor that portrays him, Hugh Jackman. This is despite the fact that Jackman retired from the role, which he portrayed since the first X-Men film back in 2000, in the 2017 film 'Logan'. He was briefly featured in 2018's 'Deadpool 2' through reused and stock footage from 'X-Men Origins: Wolverine'
In January 2018, Fox removed their other X-Men Universe film, The New Mutants from April 6th, 2018 and pushed it back to February 15th, 2019. But in March 2018, due to Fox also removing X-Men: Dark Phoenix's release of November 2nd, 2018, The New Mutants was yet again pushed back to August 2nd, 2019 as X-Men: Dark Phoenix was to take the February 15th, 2019 spot, because of it completing post production first, after both films early 2018 reshoots.
Two days after Fox released the first trailer along with the first teaser poster for Dark Phoenix, they announced the scheduled release for Valentines Day February 14th, 2019, which was the date featured in both the trailer and poster, would no longer be the date of the film's opening. Instead, the film has been moved, once again, by 4 months to June 7th, 2019. Fox reportedly says that their reason for the switch, was due to the first trailer's reception from China, which had a total of 44 million viewers in it's first 24hrs. In replacement of the February 14th spot, Fox's other film, Alita: Battle Angel (2019) will release instead of it's scheduled December 21st, 2018 release, in order to better capitalize on the Chinese box office as well. Ironically, both Fox films have been delayed twice.
This movie likely prompted the definitive return of Jean Grey in the comics 15 years after her death in "X-Men #150". During this time, she appeared sporadically in Phoenix-related arcs and was replaced by her younger, time-displaced counterpart. Jean returned in the "Phoenix Ressurection" saga and as of 2018 stars in "X-Men Red" as the team's leader.
The film will be released the same year as the spin-off film The New Mutants (2019). Maisie Williams whom plays Rahne Sinclair/Wolfsbane in the spin-off film played Sansa Stark's sibling Arya in Game of Thrones (2011) (TV Series). Sansa Stark is played by Sophie Turner (Jean Grey).
Like other comic book movies Superman III (1983). Spider-Man 3 (2004) and and X-Men: The Last Stand (2006): The film is about a superhero succumbing to his or her dark side and turning evil. This is the 2nd X-Men movie which Jean Grey succumbs to her dark side and transforms into Dark Phoenix.
While the film will be released in the US as just Dark Phoenix, internationally it will be released as X-Men: Dark Phoenix. This is presumably to more clearly market the film as a sequel similar to Logan which was released in some international markets as Logan: The Wolverine and to X2: X-Men United which was released internationally as just X-Men 2.
The film will release before Fox's other X-Men Universe film, The New Mutants (2019). Unlike Dark Phoenix's original release date where the film was to release 7 months after The New Mutants's original April 6th, 2018 release date.
Mystique and Magneto were not originally intended to appear as Jennifer Lawrence implied in several interviews that she was done with playing Mystique, though she said in an interview that she had a change of heart as she didn't want fans to be confused if her character got the 'Chuck Cunningham Syndrome treatment'.
After Batman v Superman: Dawn of Justice, Hans Zimmer said he was done scoring superhero films. It's been announced that he's scoring this movie, and shortly afterward, he signed on to co-compose Wonder Woman 1984.
Jessica Chastain was assumed by virtually everyone, from media outlets to fans, to be playing Lilandra after it was announced she was playing the Big Bad of the film, but it was never explicitly stated to be the case by Fox, which led to Chastain herself revealing that she wasn't the character over social media.
The film was initially set for release on November 2, 2018, but got moved back to February 14, 2019 to accommodate reshoots and Bohemian Rhapsody (coincidentally directed by Bryan Singer) took its slot. And then it was moved back again, to June 6, 2019, just a day after its first trailer and poster (with the February 14th date on it) were released.
Angelina Jolie was rumored to have been considered for the role of Lilandra. Surprisingly enough, her estranged husband Brad Pitt was considered to play Cable in Deadpool 2. He did appear as The Vanisher, albeit not for very long.
The trivia items below may give away important plot points.
This is the third film in the X-Men film franchise in which Jean Grey becomes Phoenix. In X-Men: The Last Stand (2006), Jean Grey (Famke Janssen) returned as Phoenix after she remained behind to allow the X-Jet to take flight and escape a flood of water, drowning her in X-Men 2 (2003). She also became the Phoenix at the end of X-Men: Apocalypse (2016) .
It's rumored that Dark Phoenix will be the final installment of the X-Men film franchise and that the X-Men film franchise will be rebooted. In early 2018 it was announced Disney had bought 20th Century Fox and that the X-Men will be brought into the Cinematic Marvel Universe. Disney also owns Marvel Studios.