I absolutely loved this movie. I read some other reviews after watching it and I got some things out of this that not everyone else did. I have three kids and got to be a single mom for a large part of their lives. I thought that this perfectly captured the feeling of desperation you can have about your children's survival and success, that you'd do ANYTHING to make that happen.
Also, she never rests, she never gets to stop, she's doing the things she's doing at top speed, no matter how painful or uncomfortable or inconvenient, all the way through, which is completely being a mom, even in this unusual context. Other people keep making problems and messes she has to handle that upset her careful apple cart just as such things do every mother's from humans to starlings. I don't know whether that was intentional but I really, really hope so.
The reviewer on Roger Ebert's site suggested the story should have been done from the hijackers' viewpoint - instead of the mother and her son - and I say he couldn't be more wrong about that. That would have made this just like every other flat, simplistic and boring action film we've seen a millions times, a plot out of Ye Olde Hacke Plot Drawer, of a bunch of guys and a monster, and lost the amazing, very unique human focus and viewpoint it had.