Never leave luggage unattended in an airport. For safety reasons, unattended luggage is considered a threat and is often confiscated or sometimes even destroyed by airport security.
Many carry-on prohibited items are self-explanatory, such as firearms and knives. However, many common items are also prohibited; these include box cutters, aerosol cans, torch lighters, tools over 7 inches in length and sports equipment such as pool cues and baseball bats.
Because everyday containers of liquids and gels can be clever disguises for explosives, strict rules are enforced on them. Regulations stipulate that containers of liquid or gel must be three ounces or smaller to be carried on a plane. Baby formula and food, breast milk and medication can be carried on in reasonable quantities that exceed three ounces, but must be declared at check-in.
