He was banned from an airline in 1998 for smoking and swearing and lost several teeth in a punch-up with German police in 2002.

So has Liam Gallagher, notorious frontman for the defunct Oasis, finally grown up?

Well, sort of.

We get to see another side of the 46-year-old singer in the documentary “Liam Gallagher: As It Was,” in theaters Sept. 13.

The camera follows the Manchester lad as he tries to forge a new path after the 2009 breakup of Oasis — the stadium-filling band he formed with his brother, guitarist-songwriter, Noel.

Liam’s post-Oasis group, Beady Eye, fizzled, but he’s set to release an anticipated sophomore solo album on Sept. 20.

“As It Was” showcases a different Gallagher than the one endlessly chronicled in British tabloids.

“Initially, I was surprised just that he was a very nice guy,” co-director Gavin Fitzgerald tells The Post. “He’s very flippant, he’s hilarious, he’s a big personality. He’s also a lot more chill.”

This is a Liam who enjoys an early-morning jog while on tour almost as much as a pint. He’s also a proud dad to two teenage sons (shown fleetingly), as well as a daughter that he sired back in 1997, with whom he recently connected for the first time.

He’s reflective of his success (as reflective as you can be while using the C-word, at least) and regrets not spending more time with his mother.

He is also, in moments, somewhat spiritual. While revisiting the childhood room he shared with older brother Noel, Liam is suddenly grateful to whatever forces turned him from a teenage wastoid into a rock star.

“Life’s magical when you think about it,” Gallagher says in the film.

One thing he hasn’t yet made peace with is Noel. The feuding siblings haven’t spoken in years and, despite Liam’s public potshots at his older bro, it’s clear the rift is painful.

“When Noel left the band, that hurt him,” Fitzgerald says. “Ultimately, they’re brothers and he misses him.”

Noel, 52, may feel differently. He refused to be interviewed and didn’t allow any Oasis music (most of which he wrote) to be used in the movie.

Liam, whom his brother once called the “village idiot,” seems to think the best revenge is his own personal happiness.

“Noel Gallagher, I don’t think he’d be too happy with the way it’s going for me at the moment,” Gallagher says in the film. “I think he’d be sitting there thinking, ‘This f - - king … what’s going down here, you know what I mean?’ ”

Liam’s 2017 solo album “As You Were” debuted at No. 1 in the UK and marked a comeback for him. The singer also recently got engaged to his former personal assistant, Debbie Gwyther, whom he says gave him the confidence to write his own songs.

But it’s not all Champagne and supernovas.

Gallagher seemingly grabbed Gwyther by the throat during a fight at a London restaurant last year (although the couple denied it) and, earlier this summer, apologized for sending threatening texts to Noel’s teenage daughter.

“He’s got a bit of an edge, but he has a heart of gold,” Charlie Lightening, Gallagher’s friend and the film’s co-director, tells The Post. “He’s still got that hard side, but if you expect him to be Liam Gallagher onstage, there’s got to be a bit of fire.”