Action heroes with nothing to lose are the best kind, perhaps the only kind worth watching. In the opening seconds of Jaume Collet-Serra's Non-Stop, Liam Neeson's federal air marshal Bill Marks slumps in his parked vehicle, sloshing a few glugs of whiskey into a paper cup and fingering a snapshot of an adorable tot. In movie shorthand, everything he stands to lose or has already lost is there in that photograph, and Neeson plays to it as if it were a big-name costar. Somehow, this fine and serious actor has reinvigorated his career in middle age by becoming an action hero. He has the face, noble and sad, of a wounded lion. If only Non-Stop were worthy of him. Neeson does nearly everything right in this terror-in-the-skies thriller. Just after takeoff, Marks receives a mysterious text telling him that if a kajillion billion dollars (or thereabouts) isn't wired into a special account within 20 minutes, someone on the plane will die. Marks takes action immediately, but neither he nor we can be sure it's the right action. He does some smart things -- like enlisting new acquaintance Jen Summers (Julianne Moore) to help him scan video surveillance screens to see which passengers in the cabin to might be using their fingers and thumbs to send the offending messages -- and some very dumb things, things that in real life would incite instant panic among the passengers. The script is an atrocity in which dumb stuff happens without a modicum of logic. Nobody's demanding an action-thriller plot that's 100 percent plausible. But is 55 percent too much to ask?