This is high concept film done wrong. The premise - Liam Neeson playing detective AND kicking terrorist ass within the confined, claustrophobic setting of a plane sounds promising enough.
Sadly, the movie is deeply stupid. The plot is ramshackle, Neeson is flat and wooden - both arguably predictable results. The biggest sin of Non-Stop is that it fails to make use of its setting,which was the one selling point differentiating Non-Stop from all the other Neeson action flicks. However, the fact that they're on a plane really only contributes to one set piece during the climax of the movie. Everything else is piecemeal and could easily take place in literally any setting.
In short, if you're looking for a unique action-thriller look elsewhere. If you are simply looking for what equates to Unknown 2 then you might be happy.