When you're puzzled over what you're allowed to carry onto a flight, think 3-1-1: Each liquid or gel must be in a container that's three ounces or smaller; all must be placed in one clear, quart-size zip-top bag; only one bag is allowed per passenger (tsa.gov/311). Or not: Packed amid all our test containers was a four-ounce bottle of moisturizer that no one looked at twice.