As of December of 2010, the United States Transportation Security Administration (TSA) allows passengers to bring liquid, aerosols and gels on board commercial aircraft, but in limited quantities. However, anything flammable or dangerous is prohibited from being brought on board.
The administration allows bottles that contain 100ml of liquid or less, and all bottles must fit into one quart-sized, clear, plastic, zip-top bag. Each passenger is only allowed to carry one such bag in their carry-on. However, if you are unsure about the regulations, it is always safer to pack any liquids with your checked luggage.
Any liquids that must be brought on board in excess of the carry-on limit have to be declared with airport officials at the checkpoint. This includes medications, baby formula and food, and breast milk.
That TSA's rules regarding liquids on aircraft don't necessarily apply to all airports around the world. Passengers traveling internationally should check with airline officials ahead of time to make sure they understand the regulations for liquids at foreign airports.
