For most people there’s no joy in sucking down recycled oxygen while hurtling above the clouds. The free drinks and freshly baked cookies in business might be nice. (I wouldn’t know.) For most of us, though, air travel largely invokes the indignities of the stockyard, complete with the crowding and pushing, the endlessly long lines, hovering handlers, carefully timed feedings, a faint communal reek and underlying whiff of peril. The skies rarely seem friendly anymore, but to Ryan Bingham, the corporate assassin played by George Clooney in the laugh-infused stealth tragedy “Up in the Air,” they’re so welcoming, he might as well be home.