Sir Ridley Scott believes there is more ''mileage'' in the 'Alien' series.

The 82-year-old director helmed the original film - which starred Sigourney Weaver and Sir John Hurt - in 1979 as well as prequels 'Prometheus' and 'Alien: Covenant' and he explained there are still stories to be told in the sci-fi franchise.

Ridley told the Los Angeles Times newspaper: ''I still think there's a lot of mileage in Alien, but I think you'll have to now re-evolve.''

The 'Gladiator' filmmaker added suggested a new story could explain how the deadly Alien was set loose on the Nostromo ship in the original movie.

Ridley explained: ''What I always thought when I was making the first one (was) why would a creature like this be made and why was it travelling in what I always thought was a kind of war-craft, which was carrying these eggs. What was the purpose of the eggs?

''That's the thing to question - who, why, and for what purpose is the next idea, I think.''

It was reported last year that Scott was returning to the franchise to helm a third prequel and he admitted he jumped at the chance to work on a new project.

He said: ''They sent me a script and I read it. I loved it. I was in Hollywood within 32 hours.''

Scott had previously cast doubt over the future of the series after this disappointing box office performance of 'Alien: Covenant' in 2017 and hinted that the future projects would focus on artificial intelligence.

He remarked: ''I think the beast has almost run out, personally.

''I think the evolution of the alien himself is nearly over, but what I was trying to do was transcend and move to another story, which would be taken over by AIs.''