United Airlines International baggage allowance has some rules about the checked baggage of its customers. Security restrictions and rules for travelers' carry-on have been established by United Airlines' baggage allowance policy. Specific United Airlines baggage fees allow liquid to be carried inside the flight. Customers flying out of any US airport may transport carry-on luggage through security and board the plane with:-Trial-size liquids, Every liquid item having 3.4 ounces or less.