Liam Neeson, unlike, say, Arnold Schwarzenegger or Sylvester Stallone or Bruce Willis - contemporaries all - was not born an action hero. Schindler's List, Michael Collins, Husbands and Wives, The Mission, Kinsey . . .. Neeson, with his broad-shouldered earnestness and husky Irish inflections, has been at this business, seriously, for a long time.

But since 2008, when Neeson took on Taken, playing a retired CIA agent who uses his special-ops skills to rescue his daughter, abducted by Albanian baddies, the actor has been making movies, and money, as a sad-eyed and improbable defender of just causes, a gentlemanly tough guy who does not brook villainy, especially when it affects his family, his loved ones.

Non-Stop finds Neeson at it again, although in circumstances that test credulity, and appear to test the mettle of the man himself. Can he stand up to the rickety ludicrousness of this airplane-hijacking thriller, which exploits our fears of post-9/11 travel? Can he make convincing the boozy, rattled caricature he's been given to play?

That would be Bill Marks, a U.S. air marshal assigned to a New York-to-London flight - undercover, of course - who heads straight for the lavatory once the jetliner is aloft. Not to relieve himself, but to have a gulp of whiskey and a cigarette (duct tape over the smoke detector). Back in business class, he chats up his neighbor, a frequent flier played with eyeglasses and a wry, inquisitive air by Julianne Moore. And then the text messages start coming: Someone on the plane knows who he is, and is demanding $150 million, or else he, or she?, will start killing passengers, one every 20 minutes.

What's a sleep-deprived, alcoholic federal agent, haunted by personal tragedy, to do? And how to identify the culprit among all the passengers? Good thing he's got flight attendant Nancy (Michelle Dockery, Lady Mary of Downton Abbey) on his side.

Or does he?

The catch, and the ostensible suspense mechanism, of Non-Stop is that all signs point to Bill himself as the hijacker. The account the money must be sent to, it turns out, is his. And the way he's barreling down the aisles, barking orders, poking his handgun, well, he's scaring everybody. He's the Hitchcock innocent, wrongly suspected and trapped 35,000 feet in the air. Bill has to find the real perp, and save the planeload of travelers, especially that cute little girl with the Paddington Bear.

Good thing Denzel Washington's drug- and drink-rattled Flight pilot isn't at the controls! (Linus Roache and Jason Butler Harner are in the cockpit, and 12 Years a Slave Oscar nominee Lupita Nyong'o is part of the flight crew - with maybe three lines of dialogue.)

Directed by Jaume Collet-Serra, who steered Neeson through the not-quite-as-implausible amnesia thriller Unknown a few years back, Non-Stop gets increasingly far-fetched as the jet makes its way across the Atlantic. Certainly, there are more red herrings on the plane than there are in the sea below. And Neeson has to stare down every last one of them.

Non-Stop ** (Out of four stars)

Directed by Jaume Collet-Serra. With Liam Neeson, Julianne Moore, Lupita Nyong'o, Michelle Dockery, and Nate Parker. Distributed by Universal Pictures.

Running time: 1 hour, 46 mins.

Parent's guide: PG-13 (violence, profanity, adult themes)

Playing at: area theatersEndText