Non-Stop brackets a thrilling middle sequence between two disappointing – but thankfully brief – acts. Your enjoyment of the film will depend pretty much entirely if you can forgive the silliness of the final act. But make no mistake, this whole film is remarkably silly – that’s the point! It’s simply that the second act’s non-stop (yes) momentum and tension should keep you engaged enough to distract you from the details of the ridiculous plotting. I recognised fairly early that there was never going to be a satisfying answer to the myriad questions posed by the film, so I had a great time with Non-Stop; depending on your tolerance for outlandish absurdity, your mileage may vary.

The first act starts simply, despite director Jaume Collet-Serra’s inexplicable attempts to throw every stylistic trick in the book at it (sorry, hanging out in the departure lounge isn’t tense no matter how much ominous music and grainy, shallow focus cinematography you throw at it). Bill Marks (Liam Neeson) is introduced as the standard grizzled hero, guzzling down whiskey while caressing a photo of his young daughter. But don’t worry, dear audience, this drunk is a good dude! We know this because he picks up a young girl’s forgotten doll and because he’s played by Liam Neeson.

Things get more complicated pretty quickly. It turns out Marks is an air marshal, though his partner (Anson Mount) doesn’t have much faith in his abilities (because he’s a drunk, remember). He receives ominous messages on his private air marshal network that quickly turn into threats – deliver $150 million dollars or, in twenty minutes, someone will die.

This stage of the movie is easily Non-Stop’s strongest, using the inherent tension of a closed-room murder mystery setting to hold your attention. The plotting is pitch perfect, encouraging you to ask questions like “Is Marks doing the right thing?” or, more often: “Who’s sending the messages? Is it the attractive redhead (Julianne Moore) sitting next to Marks? The creepy guy (Scoot McNairy) who bummed a smoke off him at the network? The stony-faced bald dude (Corey Stoll)? The friendly, perhaps-too-understanding stewardess (Michelle Dockary)? The token guy of Arabic descent (Omar Metwally)?”

Non-Stop’s screenplay cleverly messes with audience expectations here (for example, it doesn’t even try to pretend the Arabic doctor is a real suspect, because they never are in these films). Every time the evidence seems to mount, suggesting that it has to be so-and-so, they turn out to be the next victim, and the twenty minute clock starts again. It’s gripping without being repetitive, and things escalate. Apparently the bank account is in Marks’ name. The TSA begins to worry that Marks isn’t trying to save the plane, he’s trying to hijack it.

The best sequence of the film is a bravura single-shot sequence that lasts for about ten minutes. Technically it doesn’t even try to hide its digital trickery (the camera moves through solid doors and even outside of the plane), but as Marks desperately searches potential suspects for evidence as the twenty minute mark approaches, it’s utterly captivating where it could easily have been tedious. This sequence is elevated by Marks’ increasingly desperate behaviour. We wonder how long we would tolerate this kind of behaviour from someone just because they’re carrying a gun and a badge.

Questions about how far we trust authority get conflated into issues around terrorism, airport security and clumsy evocations of September 11. Non-Stop is too politically muddled for this to hold any water – the filmmakers don’t want to upset anyone by actually taking a firm position one way or the other on these issues – but at least there’s something deeper than guns and bombs going on. It’s not entirely ineffective, though; when a coterie of passengers charge Marks to try and reclaim the plane, it’s the kind of action sequence these thrillers so rarely engage in, where there’s no clear “goodies” or “baddies” to root for.

The escalation continues, with the threat getting more serious and the film getting much sillier. If you’re still taking the movie seriously by the time a bomb is found hidden in a block of cocaine, then I don’t know what to say to you. Yes, the final act reveal of the villain’s identity and motivations is laughable, but Non-Stop doesn’t expect you to treat it as anything else (after the villain’s agenda is explained, Neeson memorably responds with: “You should’ve just handed out pamphlets, it would have been a lot easier.”). It also zips through the conclusion, powering through all the exposition and requisite unbelievable action in record time.

In retrospect, the entirety of Non-Stop is utterly ridiculous. The reason its second act is its most successful is that it distracts you into worrying about questions like “Who’s the bad guy?” when a number of other questions – “Why does every victim die exactly at the twenty minute mark?” “Why would a known unstable alcoholic be hired as an air marshal?” “How on earth did the terrorist coordinate this so perfectly?” – would reveal the thinness of the narrative.

Non-Stop succeeds as a thriller if you can disregard the contrivances of the story, buckle in and enjoy it for the bumpy ride that it is. Its appeal is mostly thanks to the cast. Liam Neeson has his Danny-Glover-in-Lethal-Weapon schtick down to an artform by now, and the rest of the cast is similarly overqualified (special mention to Oscar-winner Lupita Nyong’o, who gets to do absolutely nothing here). Sure, if you’re looking for a film that engages you intellectually – whether in its narrative or its themes – you’re out of luck. But if you’re looking for an old-fashioned thriller that keeps your attention for at least ninety minutes of its running time … what about Non-Stop?