Flight Risk is a short, swift thriller directed by Mel Gibson and starring Mark Wahlberg as the bad guy.

Despite a measly 21% rating at Rotten Tomatoes, the movie does its job reasonably well, managing to hold our attention despite a poorly thought-out script.

Downton Abbey’s Michelle Dockery plays Madolyn Harris, a U.S. Marshal charged with escorting a long-sought mob witness (Topher Grace) from his remote hideaway in Alaska.

So Winston and Harris take off for Anchorage in a single-prop Cessna flown by a loquacious and somewhat abrasive pilot (Wahlberg).

Before long, both passengers discover that the apparent redneck flyer is not really their assigned pilot. Nope; he’s actually working for the mob-boss against whom Winston will testify. And he certainly doesn’t plan for that frightened stoolie to arrive safely at his destination.

So Flight Risk is one of those claustrophobic, one-set thrillers with a small cast and a vicious villain. Indeed, after somehow overcoming the original pilot, “Booth” is not going to be cowed just because Harris is the one with a gun.

Besides Gibson, I suppose the main draw here is whether Wahlberg can pull off a bad guy. But he’s been so tough in heroic roles that there really wasn’t much doubt.

He’s the kind of villain who’s always able to revive for more havoc — even if he’s been shot, tied up, handcuffed or bashed over the head with a fire extinguisher.

Sadly, the script by newcomer Jared Rosenberg doesn’t serve Wahlberg well. Though Rosenberg has a dandy set-up, the strong but slimy Booth is almost a caricature of other baddies: A bizarre, half-baked blend of balding creep, skilled assassin and jail-bird homosexual, Booth never gels into anything realistic or cohesive.

Indeed, Rosenberg’s script nearly scuttles the entire film. Despite solid performances — Dockery is especially strong — none of the three main players act with much logic or consistency. And that problem permeates the action-story as a whole: It’s so loaded with plot holes and logistical absurdities that before penning this review, I wrote up a list of 8-10 annoying questions that ran to nearly 200 words.

I won’t include that here, since it’s full of spoilers; but it sure was distracting that even a non-pilot like me could pick apart the aviation scenes — and other aspects, too.

Take, for instance, the character Hasan: Coming on the radio to help Harris pilot the plane, he instantly starts hitting on her for a date later that night. I mean, really: Does this make even a lick of sense? Worse yet, Harris seems responsive to his overtures! And while we’re on this: Why didn’t Hasan ask what airport she’d left from? Given the flight plans that have to be filed, this sure would’ve yielded some vital info! And why on earth did he stop giving her advice the minute she approached the runway? Wouldn’t landing be the hardest part??

It’s a testament to the three performers — and to Gibson, whose action resume includes Hacksaw Ridge and Braveheart (for which he won a directing Oscar) — that we stay involved despite all this nonsense. Indeed, Flight Risk remains quite suspenseful right up through its somewhat hare-brained climax.

The most irritating thing is that none of the illogical stuff was vital to the plot and could easily have been tidied up for a more convincing tale — one that might’ve stood the test of time as a decent B-picture.

It’s still fun — but actual pilots in the audience may find it living up to its title; they’re likely to bail out long before Gibson finally lands the plane.