What is “Saturday Night Live” never made it to air? According to director Jason Reitman’s “Saturday Night,” that almost happened.

The biopic dramatizes the lead-up to the comedy variety show’s inaugural episode in 1975, in which then-green Lorne Michaels (Gabriel LaBelle) must cut down a three-hour show starring other unknown 20-somethings, most of whom would later become comedy legends.

NBC, led by executive David Tebet (Willem Dafoe), shows great interest in this creative yet unproven endeavor. As such, Tebet gives a vote of confidence in Michaels and encourages him to achieve his dream at any cost, though it’s later revealed that SNL was only given the green light because of a contract dispute with Johnny Carson.

Some executives were even counting on the show failing.

While well-spoken, Michaels doesn’t inspire much confidence at first. His unwillingness to cut down on material in the minutes leading up to the broadcast almost derails it, and he lets his stars walk all over him. He even wastes precious time — minutes before they go to air — chasing down John Belushi (Matt Wood), who refuses to sign his contract.

But a lot of that chaos can be contributed to the fact that Michaels had never directed a live show like this before, and he does learn on the fly. He realizes just in time that, as the head of this production, he needs to make tough decisions even if it will make some unhappy, for the sake of the show.

Michaels is bolstered by having one of the greatest casts of all time: Chevy Chase (Corey Michael Smith), Dan Aykroyd (Dylan O’Brien), Gilda Radner (Ella Hunt), Garrett Morris (Lamorne Morris), Jane Curtin (Kim Matula), Andy Kaufman (Nicholas Braun) and, of course, Belushi. These people are all comedy royalty today, but they were young, ambitious and — most importantly — cheap back in 1975.

Outside of the main cast, Michaels also had a stacked deck. Episode 1’s host was standup legend George Carlin (Matthew Rhys), and he had Al Franken (Taylor Gray), Tim Davis (Mcabe Gregg) and Alan Zweibel (Josh Brener) in his writers’ room — the last of which he found at a bar (this did actually happen in real life, but not on the eve of the broadcast). He even had “Muppets” creator Jim Henson (Braun) on hand as a puppeteer.

Despite its lack of a solid plan, SNL had so much concentrated talent in one place that it almost couldn’t fail.

That’s also something the film’s cast communicates pretty well; Chase is framed early on as a star by Tebet, and Rhys captures Chase’s blind confidence brilliantly. O’Brien also gets Aykroyd’s unique mannerisms down, and most of the cast follows suit; everyone gives a very good impression of their respective characters, which allows them to capture a sliver of the real-life chemistry these people had on SNL.

The film also shows the scummy side of show business, primarily when Carson (Jeff Witzke) tries to demoralize Michaels in a phone call and when television legend Milton Berle (J.K. Simmons) sexually harasses Chases’ girlfriend, Jacqueline Carlin (Kaia Gerber).

Chase is almost insufferable throughout the film on purpose (the real-life actor is notorious for being hard to work with), but he’s exceptionally funny and ultimately does his job. Berle serves as an excellent foil that gets us to root for Chase; Berle is mad with power and thinks his past success on TV gives him a license to do whatever he wants, including pulling out his penis in front of Chase and Jacqueline Carlin.

Chase ultimately has the last laugh; his star is rising, and, despite his arrogance, Berle’s is fading. Because of his “Vacation” movies, Chase would go on to occupy a unique corner of the American psyche; generations will know his name for years to come because of them. Nobody young today knows who Berle is.

“Saturday Night” is an exceptionally well-made love letter to SNL and this era of comedy. For so many, the show has been a key inflection point that launched their careers into the stratosphere, and it all happened with this first show.

It is, however, important to take all the events in the film with a grain of salt. It does combine several real-world events and dramatically plays up others. But that’s par for biopics; nothing you watch in this genre of film should be taken as fact. At best, they capture of the spirit of their subjects.

I highly recommend “Saturday Night,” even for those that might only passively watch SNL.

Unlike so many other films in this genre, like “A Complete Unknown” and “One Love,” (the recent Bob Dylan and Bob Marley biopics) which are completely inaccessible to outsiders, this movie communicates effectively what made SNL so different from its peers and what made it so hard to pull off.

If you’ve seen one episode of SNL or 100, you’re going to have a great time.

“Saturday Night” gets a 9/10