Remember when you had to take off your shoes at every checkpoint, and Southwest let you sit wherever you wanted? Both are now things of the past, and so is the old rule about what happens if you forget your ID. Airports and airlines have quietly rewritten the rulebook, changing everything from checked bags to how you cross a border in Europe. If your last flight was a while ago, prepare for some real surprises. Here are 10 changes worth knowing before your next trip