Sources tell The Hollywood Reporter that the style and vision of Lord and Miller clashed with that of Lawrence Kasdan, the legendary screenwriter behind the classics Empire Strikes Back and ?Raiders of the Lost Ark, who also wrote, with his son Jon Kasdan, the script for the Han Solo stand-alone set (for now) to be released in 2018.

Lord and Miller (21 Jump Street, The Lego Movie) have a comedic sensibility and improvisational style while Kasdan favors a strict adherence to the written word — what is on the page is what must be shot.

The creative clash, according to one insider, also came down to differences in understanding the character of Han Solo. "People need to understand that Han Solo is not a comedic personality. He's sarcastic and selfish," said that source.

The friction was felt almost immediately after the movie began shooting in February, sources say, but the directors thought it could be worked through. Kennedy, the producer and head of Lucasfilm, decided to back her lifelong colleague, who shaped much of Solo's character in Empire and ?Return of the Jedi and who had a specific tone in mind for the new movie. The duo also didn't feel they had the support of producer Allison Shearmur, who was acting as Lucasfilm's representative on the London set.

Lord and Miller, who had relocated to London with their families for preproduction and production of the movie, were said to have been blindsided by the firing, which they learned about Monday, according to one source, although another disputed that account.

The production had gone on a short hiatus to review what had been shot and to clear the air.

"Unfortunately, our vision and process weren't aligned with our partners on this project. We normally aren't fans of the phrase 'creative differences' but for once this cliche is true. We are really proud of the amazing and world-class work of our cast and crew," Lord and Miller said in a statement released Tuesday.

Lucasfilm and owner Disney have already targeted their replacement, although the companies are keeping mum.

Ron Howard is one of the names that has emerged, according to sources. Joe Johnston, who directed The Rocketeer and Jumanji, has been mentioned as another possible candidate. Others suggest that Kasdan, who has directed movies like ?The Big Chill and Silverado, could step in as he is already in prime position to know what needs to be fixed. That move could be complicated by DGA rules preventing someone already working on a film from taking over for a director who is being replaced except in the case of a short-term emergency.

It is expected that a new director will spend the next several weeks, with the production shut down, going over what Lord and Miller have shot, reedit what they've filmed "and go from there," according to one source.

According to some observers, Lucasfilm should have known going in that a clash of tones could occur given Lord and Miller's previous work. But this is not the first time that Disney and Lucasfilm have had to take drastic turns on Star Wars movies. Last summer, the companies sidelined Gareth Edwards, bringing in Tony Gilroy to rewrite and direct substantial reshoots of Rogue One: A Star Wars Story, a move that happened only five to six months before the movie was released. Rogue One proved to be a massive hit, both financially and critically.

The studio now is more than willing to flex its muscle, and spend chunks of money, to protect the Star Wars brand and to ensure that it is not tarnished by a movie that doesn't deliver what fans want.

Lord and Miller's next move is not immediately clear, but already rumors are circulating that the pair could return to The Flash, Warners' movie about the DC Comics hero which they had been attached to helm several years ago. The project is currently on the hunt for a director.