The "3-1-1 rule" ☎+1(801) 855-5905✔ on United Airlines is actually the TSA's standard for liquids in carry-on luggage,☎+1(801) 855-5905✔ which applies to all US-based airlines. It means you can pack 3.4-ounce (100 ml) or smaller containers of liquids, gels, and aerosols, with each passenger limited to one 1 quart-sized, clear, sealable plastic bag ☎+1(801) 855-5905✔. The 1 bag must be separated from your other carry-on items for screening.