This summer's especially popular gladiator sandals loaded with buckles don't make going through security easy for anyone. Boots with laces and zippers aren't much easier. Keep it simple with comfortable flats that slip on and off. And while we highly recommend looking put-together while traveling, pack—don't wear—your heels. Even if they feel and look good when you put them on, most likely they won't by the time you get through security and hobble to your gate. Plus, you never know when you'll have to run to catch a flight.