Flammable or hazardous liquids, such as gasoline, paint or pepper spray, are not allowed on airplanes in any quantity. Most common lighters are allowed, but they must be in checked baggage.
Alcoholic beverages are also restricted. If they are over 140 proof, they cannot be transported on an airplane. Alcohol that is less than that is allowed, but it has to be packed in checked baggage. Open containers have to be re-closed, and there may be additional restrictions for people bringing alcohol through customs.
Most liquids have to be packed in travel-size containers that are 3.4 ounces or smaller, and they must be packed in quart-size zip-top bags. This rule does not apply to liquid prescription medications, which can be carried in any quantity needed for the trip and do not have to be packed in a bag. People who are traveling with young children are also exempt from those rules if they need to bring formula, breast milk or juice onto the plane. The exemption also applies to necessary supplies for storing the medication or formula, such as ice packs to keep it cool. These items may be selected for additional screening.
People who are unsure of whether a liquid is allowed should contact the Transportation Security Administration or the airline they plan to use before going to the airport.