The first full day of a strike by Sag-Aftra had an immediate effect on Hollywood, as the industry ground to a halt over a contract with producers that would cover such wide-ranging issues as compensation and the future of AI in film and television.

Whereas the writers’ strike, which has seen the guild’s nearly 20,000 members out of work since early May, promptly shuttered late-night variety programs and writers’ rooms and delayed release dates for many film and TV shows, a simultaneous strike by Sag-Aftra’s 160,000 members has the potential to bring Hollywood to a full standstill.

Actors and writers began picketing outside various studio and streaming service headquarters on Friday – four locations in New York and eight more in Los Angeles, with such signs as “Logan Roy would pay us more”; “Your poor Montana ranch!”; “I’m trying to pay my rent, not my third and fourth mortgage and fuel my private jet!”; and “ChatGPT can suck my D.”

The strike – the first time the actors have joined writers on the picket line since 1960 – immediately ceased promotional work for several major summer films, which was already hindered by the absence of talkshows. According to strike guidance, members will not be able to attend premieres, do interviews for completed work, attend award shows or film festivals, or promote projects on social media while the strike is in effect.

The strike canceled the New York red-carpet premiere of Oppenheimer, Christopher Nolan’s biopic about the creator of the atomic bomb. On Thursday, the film’s cast, including Cillian Murphy, Emily Blunt and Matt Damon, left the film’s London premiere early, when the strike was called. (Damon told Deadline that the strike will affect his new production company founded with Ben Affleck.) The cast of this month’s other hotly anticipated film, Greta Gerwig’s Barbie, also wrapped its promotional campaign early. “I very much am in support of all the unions and I’m a part of Sag, so I would absolutely stand by them,” the film’s lead, Margot Robbie, told reporters at the London premiere.

One of the first major productions affected was Deadpool 3, which paused filming on Thursday as the strike got under way, only days after Marvel revealed a first look at the set with photos of the stars Ryan Reynolds and Hugh Jackman costumed as Deadpool and Wolverine, respectively. As the script was already locked, Deadpool 3 was able to continue production during the writers’ strike. But the film’s original May 2024 release date now seems in jeopardy due to the production halt, a sign of the Hollywood stasis to come.

HBO’s blockbuster series House of the Dragon, however, will continue filming in the UK due to local union rules, as first reported by Variety. The majority of the actors on the Game of Thrones prequel, currently filming its second season, are from the UK and thus under contracts governed by the UK local union, Equity. The series is technically allowed to continue filming as Equity members are not legally permitted to strike in solidarity with US actors. In strike guidance provided by Equity hours before Sag-Aftra officially declared a walkout, the union, the 12th largest trade organization in the UK, said it would “support Sag-Aftra and its members by all lawful means”.

A strike could also torpedo major summer and fall film festivals, which are now in wait-and-see mode. Glitzy photo opportunity-oriented festivals like Venice, which is set to begin on 30 August, could be held without major Hollywood stars. The Toronto film festival, held in September, said in a statement to Deadline on Thursday that organizers will “continue planning for this year’s festival with the hope of a swift resolution in the coming weeks”.

Broadway will remain open, as Sag-Aftra does not represent stage actors. But on Friday, the president of Actors’ Equity, which represents stage actors and stage managers, urged members to “proactively and aggressively avoid breaking” the Sag-Aftra strike by inadvertently crossing the picket line. The guild president, Kate Shindle, encouraged members to contact Sag-Aftra with any questions about potentially struck work, and added: “Know this: the other side will try to pit us against each other to keep churning out content. Don’t fall for it.”

At the heart of the negotiations is what many members have referred to as an existential question over the future of AI in replacing writers or generating unapproved likenesses of actors, among other concerns. The Alliance of Motion Picture and Television Producers (AMPTP) said it offered a “groundbreaking AI proposal which protects performers’ digital likenesses, including a requirement for performer’s consent for the creation and use of digital replicas or for digital alterations of a performance”. But Duncan Crabtree-Ireland, Sag-Aftra’s chief negotiator and national executive director, denounced that proposal on Thursday for only paying background performers for one day of work in exchange for the rights to their digital likeness “for the rest of eternity with no compensation”.

“If you think that’s a groundbreaking proposal, I suggest you think again,” he added.

In the hours after the strike was called, numerous Hollywood stars, including Jamie Lee Curtis, Bob Odenkirk, Cynthia Nixon, Sheryl Lee Ralph and Josh Gad, expressed public support for the dual work stoppages.

George Clooney has also backed the strike, and said in a statement on Friday that “actors and writers in large numbers have lost their ability to make a living”.

“This is an inflection point in our industry,” he said. “For our industry to survive that has to change. For actors, that journey starts now.”