The TSA‚ 3-1-1 rule restricts the amount of liquids travelers can bring in their carry-on luggage to containers no larger than 3.4 ounces, or 100 milliliters. All liquids must be stored in a single, quart-sized, clear plastic bag. This rule applies to items like toiletries, cosmetics, and beverages.

It was introduced in 2006 after a foiled terrorist plot involving liquid explosives, and it remains a key security measure for air travel.While many travelers find the rule frustrating, it's important for ensuring safety on flights. Some exceptions exist, such as for medications, baby formula, and breast milk, which are allowed in larger quantities. To avoid delays at security, it's advisable to follow the 3-1-1 rule and pack accordingly.