Jason Reitman's "Up in the Air" is worth seeing just for the opening credits, a soaring shifting serenade to the world seen from a plane window. It's thrilling and thrillingly beautiful, just as flying is (and - as my inner cinemaphile feels obliged to add - just as watching a film is). But don't just see the opening credits; the rest of "Up in the Air" is thrillingly good, too. For the film isn't just about a tiny class of professional travelers who feel at home in planes, airport lounges and hotels, but about all of us who have a second home in that floating world. I do, though I fly less than I used to, and I recognized the so bearable lightness of such being with pleasure, even delight (such a smart film!). Then with pain and even grief.