Insights into the film's themes
The film succeeds as an amusing social commentary and a deep love story, as well as a visual/musical delight. I'll only focus on the deep love element. It's been noted that the story originated from writer/director Sofia Coppola's experience with an aging actor when she was younger, possibly Harrison Ford. Sofia is obviously Charlotte, while Charlotte's husband is Sofia's ex and Anna Faris plays the role of the other woman, which would be Cameron Diaz in real life. So there's a lot of reality in the picture.
But it's not just a cathartic piece. Sofia has some potent insights to offer on the nature of true romantic love. For one, love transcends age difference (Bob is about 35 years older than Charlotte). For another, it's possible to be married and experience romantic love for another. Not that this ever justifies adultery, it's just a fact. As the story progresses you'll see how comfortable Bob and Charlotte are with each other, how they look into each other's eyes, the windows of the soul, in a profoundly naked sense.
This can happen in the flash of a moment where the two people just KNOW, or it can take place over a period of time, as is the case with Bob and Charlotte (which is a handful of days). They see the same things and speak the same language, and I don't mean English. But this presents a conundrum for Bob. He COULD take advantage of Charlotte because she's so lonely in a sea of people, which is one of the movie's themes; she's also inexperienced and vulnerable. Will he or won't he take advantage?
***SPOILER ALERT*** Don't read further if you haven't seen the film.
If Bob loves Charlotte so much, not to mention his wife & kids, why does he have a one-night stand with the lounge singer? Bob slept with her to release sexual tension that had been building up between him and Charlotte. This was a moral failure, but keep in mind that he was drunk (another failure but, have pity, he was going through a mid-life crisis). While all this is obvious, it goes deeper...
Bob could have taken advantage of Charlotte if he wanted to but didn't because he genuinely loved her, which is revealed at the end. Bob could sleep with the singer because he didn't love her (not that it justifies his actions). Simply put, true love transcends sexual expression and sexual union does not equal love.
The ending is powerful and tear-inducing. No CGI, explosion or action stunt can compare. It's just an older man and a too-young woman embracing in the midst of 20 million strangers. Tears flow, kisses are given and unheard words are whispered. They could never be a couple, even if they weren't married, and they know they'll never see each other again, at least on this plane, but their love has been expressed and will be treasured for eternity.