He was the heartthrob of the early 2000s, and now Josh Hartnett is back … and battling assassins at 37,000.

We caught up with Josh and the stars of “Fight or Flight” — mainly because they weren’t trying to get away — but their movie is a pulse-pounding action thriller where turbulence isn’t the only thing trying to kill you.

“Fight or Flight” follows Lucas Reyes, a troubled American spy played by Josh Hartnett. He’s got one last chance to prove himself to his superiors, so he’s sent to find a high-value target known as “The Ghost.”

The twist? The plane is packed with international assassins ready to strike.

Josh Hartnett: “I wanted to do something in the action world for a long time, but I wanted to do my own stunts. But also, it was the tone that really hit me, that I thought, I knew exactly what Lucas had to be, and I felt like, if we could pull it off, it would be unique amongst the films that are being made these days.”

This isn’t your typical action flick. It’s full of mind-bending twists, with a side of comedy … so you could only imagine how exciting it was on set.

Josh Hartnett: “I had a fantastic stunt team around me, that was helping me kinda get through it. The camaraderie between them was fantastic, I felt like a part of the team. To be able to pull off my own stunts, it took that whole team to help me do it.”

So who’s behind the chaos of the flight? Well, that’s what has to be to figured out …while staying alive at 37,000 feet.

Josh Hartnett (as Lucas Reyes): “What the hell are you doing?”

Charithra Chandran (as Isha): “I was trying to help you!”

Charithra Chandran — yes, the “Bridgerton” breakout — turns up the heat as an unexpected hero. She says she felt all the love while doing it.

Charithra Chandran: “One of the wonderful things about why this film feels like such a privilege for me, is that it was the first time I got to do, like, proper stunts. And so, the day that I filmed the stunts, it was such a supportive environment. Like, I remember, after every take, you could hear from video village, people cheering.”

The cast tells Deco what they’d actually do in such a turbulent turn of events: fight or flight?

Josh Hartnett: “Well, I’ll fight and flight, because I’ll be on the flight anyway, so then, if I need to fight to save my loved ones or someone else that’s in trouble, I’ll fight for them.”

Charithra Chandran: “In crunch time, clearly I’m a fighter.”

For nervous flyers. I mean watchers, maybe grab some Dramamine first.

Charithra Chandran: “I think this is the kind of film that you have to see on the big screen, because it’s so high-impact, right? Like, it will just blow you away.”

Honestly, we may never fly commercial again.

“Fight or Flight” drops this Friday. Buckle up, and prepare for turbulence, with punches.