Tom Cruise's "Mission: Impossible - The Final Reckoning" powered into the Cannes film festival for its premiere on Wednesday, with first reactions saying it lives up to its steamroller hype.

With some fretting that the US$400-million epic – the eighth in the high-octane franchise – could be the last, Cruise and director Christopher McQuarrie have dropped contradictory clues about its future.

Both have also gone on a gruelling globetrotting tour to promote one of the most expensive movies ever made after being delayed by Covid lockdowns and Hollywood strikes.

But the wait appears to be worth it, according to the Hollywood Reporter, which quoted critics emerging from the first press screenings calling it "astonishing," "jaw-dropping," and "just insane."

Hours before the premiere, McQuarrie revealed Cruise – who does his own stunts – took his risk-taking a little too far during a shoot in South Africa.

The crew feared the 62-year-old star had passed out after climbing out on to the wing of a stunt biplane he was piloting alone, he told an audience at Cannes.

"Tom had pushed himself to the point that he was so physically exhausted" after spending 22 minutes being blasted by the propeller – more than twice the time safety guidelines allowed, McQuarrie told an audience in Cannes.

"He was laying on the wing of the plane, his arms were hanging over the front of the wing. We could not tell if he was conscious or not," said the American filmmaker, who has shot the four last movies of the franchise.

Cruise, a trained acrobatics pilot, had agreed a hand signal to show if he was in trouble, McQuarrie said.

But "you can't do this when you're unconscious," he added.

Cruise smiled sheepishly as the director told the story, stressing that years of preparation went into the movies, which he compared to the workings of "a Swiss watch."

But in the end, "I like the feeling (of fear). It's just an emotion for me. It's something that is not paralysing.

"I don't mind kind of encountering the unknown," insisting that "this is what I dreamed of doing as a kid," Cruise said.

The star has also been sharing other heart-stopping behind-the-scenes footage of other stunts he did for the movie on social media, including a freefall jump from a helicopter at 3,000 metres.

He is seen jumping from the chopper high over a South African mountain range and putting himself into a high-speed spin with a camera strapped to his stomach.

The blockbuster is set to ramp up adrenaline levels and promises to lighten the tone at Cannes, whose highly political opening day began with accusations that Hollywood was ignoring "genocide" in Gaza and ended with Robert De Niro lambasting Donald Trump as "America's philistine president." (AFP)