There once was a time when you did not have to be at the airport an hour and a half to two hours before your flight. Nowadays, this is standard procedure because of the time it takes to go through airport security. The airport security regulations in the United States are enforced by the Transportation Security Administration, or TSA. The security checkpoints you see in the airports in other parts of the world work in much the same way as the ones in the USA do. All people and their belongings must go through a screening, which includes running their luggage through an x-ray machine, and walking through a metal detector. Liquids and gels are not allowed to go through security except in very small quantities. Prescription liquid medicine, baby formula, diabetic supplies, and a few other special liquids and gels are allowed through the checkpoint by airport security regulations. Some items will be allowed inside your checked baggage that goes on the plane, but not in your carry-on bag that goes into the cabin with you.