The rule stated that each container of liquid, gel or aerosol — whether it’s water, shampoo or hairspray — must be 3.4 ounces (100 ml) or less, all containers must fit into one quart-sized (one-litre) clear zip-top bag, and only one bag is allowed per passenger. Since then, TSA checkpoints have borne the familiar rituals of chugging water and tossing oversized containers, and fights over what’s considered a liquid or not.
