The original fantasy movie, starring Sigourney, Zoe Saldana and Sam Worthington, was released in 2009 and followed a group of scientists exploring a new moon called Pandora. Back in 2014 when there was only three follow-up films in the pipeline Zoe revealed they would be shooting concurrently, and according to Sigourney adding another instalment hasn’t changed James’ plans.

“I think what he's been doing is trying to develop the technology. We're going to do all four simultaneously, so I think he's trying to make sure that he has really done all the groundwork so when he really starts these four we'll be able to hit the ground running,” she told Superherohype.com. “He IS experimenting. I don't know if any of that would end up in the movie 'cause it's not actually any of the story, but I'm sure he's trying to figure out how to photograph an animal in this situation, things like that, so on the day he doesn't have to waste time finding that out.”

Avatar 2 is scheduled to hit cinemas in December 2018; a later date than initially slated after James announced Avatar five earlier this year (16). But it's not clear if production will meet the deadline as Sigourney, who will be reprising her role as Dr. Grace Augustine, recently admitted work on the first sequel hasn’t even begun yet.

"We haven't started it, so I don't know how realistic that date is, but I think it's going to be very exciting,” she noted while talking to The Hollywood Reporter. “I've read three of the four sequel's scripts, and they're even more extraordinary than the first one."

The final three films are expected to hit cinemas in December 2020, December 2022 and December 2023.