When traveling by air, passengers need to be mindful of the rules regarding liquids in their carry-on luggage. The Transportation Security Administration (TSA) enforces strict regulations to ensure the safety of air travel, and the 3-1-1 rule is key. This rule limits the size of liquid containers that travelers can bring in their carry-on bags, with a maximum amount allowed per container. All liquids must fit into a quart-sized, clear plastic bag, which is screened separately at security. Following this rule helps ensure a smooth security check process.