Airport Security is the first line of defense against potential criminal activity inside the airport and on aircrafts, including possible acts of terrorism.

Inside every American airport there is a system of checkpoints where travelers are required to identify themselves with legal documentation before boarding an aircraft. Acceptable identification at these checkpoints includes a state issued drivers license or ID card, a valid passport, U.S. Military ID or a Department of Homeland Security "Trusted Traveler" card.AirSafe.com: Airport Security Issues

In 2007, the U.S. Transportation Security Administration began testing whole-body imaging machines in 19 airports across the nation. Though use of the machines is opposed by privacy advocate groups because they produce "nude" images of passengers, the machines are being hailed by the TSA as a faster, less invasive security screening procedure for passengers.

The whole-body imaging machines are operated by two security professionals to ensure privacy, one professional operates the machine while the other screens the images in a separate room. The security professional operating the machine never sees the images and the security professional screening the images never sees the passenger. As additional privacy precautions, the passengers' faces are blurred out and the total image is "fuzzy". Each image is deleted automatically after being screened.

In May 2009, privacy advocate groups asked the TSA and the U.S. Department of Homeland Security to suspend the use of whole-body imaging machines. The TSA said that precautions have been taken to ensure passenger privacy.CNN: Airport security bares all, or does it? (May 18, 2009)