Reitman previously gave us the godawful Juno but since Up in the Air is merely pedestrian and predictable I suppose that counts as some kind of progress. It's a movie where as soon as two antagonistic characters are sent on a road trip you know they will come to some kind of mutual admiration. Where the confident young hotshot will learn life isn't what she expects. Where when Clooney's character Ryan decides (on stage during a lecture no less) to surprise visit his girlfriend that she will turn out to have another life. Where an employee that threatens suicide but nobody believes her will follow through. Where when his sister mentions they can't travel anywhere on their honeymoon Ryan will eventually give them some of his hoarded airline miles.
To some degree predictability doesn't much matter since most art depends on it. Many of Shakespeare's plays dealt with stories familiar to the original audiences and Stanley Wells has noted that he even avoided many of the surprise twists often found in work by his contemporaries. What matters in Up in the Air is that Reitman is trying to create an illusion of hard-earned wisdom or at least surprise but the film is as unsurprising (and less imaginative) than, say, 27 Dresses. Apparently the idea is that we see Ryan learn how alienated he really is, how he really does need other people, which seems a little odd given that Ryan and much of the first half is basically comic despite the on-screen firings. As viewers we already know Ryan is alienated just as we know Daffy Duck has a temper problem so seeing their realization doesn't have much point. This isn't a tragedy - we aren't seeing Oedipus have a bad moment or even Falstaff hearing "I know thee not old man".
In fact one of the main problems with Up in the Air is to even consider Ryan alienated. There are after all many people who are perfectly happy in such circumstances, who don't need this intricate web of other people that the film ultimately insists is the norm. Perhaps the most interesting scene is one where Ryan has Natalie "sell" him on the idea of marriage but she sputters because she clearly has never really thought about the "why". (Can you imagine what Hawks or Sturges would have made of this material? Or going a completely different direction Mike Leigh? It's certainly unfair to compare Reitman to them but at least that shows why it's easy to say he wasn't even trying.) By the end of the film it's clear that, even despite Alex's offer of cheerful adultery, Reitman is firmly on the idea that there are no other options other than the most straightforward, mainstream one.
And that's only a problem because unlike a romantic comedy Reitman is pretending to be open-minded. Just look at the scene where Ryan has to convince his sister's fiance to go through with the wedding. Where you might expect some kind of smart dialogue or even quasi-clever argument Ryan simply drones on for a while, just as he previously had been the world's most monotonous inspirational speaker. (Which early in the film I thought was part of the joke but later wondered if there was some disconnect from the script.) An argument could be made that the fiance really doesn't need convincing, that he really wants the wedding but simply needs a push over last-minute jitters, but that's not what's in the film. Are we really supposed to think Ryan is finally being a big brother? Or that his clumsy "do you want to be alone" talk really works?
There is supposedly some kind of topicality in the fact that Ryan is hired to fire people (though the book appeared in 2001). If anything this is even more implausible and ultimately grating. We get brief talking head shots of various reactions to the firings and in one scene Ryan convincing a fired employee that he's now free to pursue his interest in cooking. Are we really supposed to think this is what happens? That the firing was a "good thing"? The only reason I suspect so is the incredibly ill-conceived sequence at the end where another series of talking heads tell us how fortunate they are to have, well, whatever/whoever it is that they have. You probably couldn't come up with a more cynically manipulative "happy" ending and if nothing else it shows that Up in the Air has absolutely nothing to say about the current economic situation or in fact about corporate America. As far as we get from the film the firings are simply something that happens like a tornado. Apart from a bit at the start about Ryan being hired because the actual managers don't have the courage, there's no hint that firings are actual decisions made by actual people and in many cases are not at all necessary - they're done to preserve profitability not to preserve the actual existence of the company. So while viewers are sold on the idea that Ryan offers a humane way to do the firings, that's as far as the film is willing to go.