Large numbers of people pass through airports. Such gatherings present a target for terrorism and other forms of crime due to the number of people located in a small area. Similarly, the high concentration of people on large airliners, the potential high lethality rate of attacks on aircraft, and the ability to use a hijacked airplane as a lethal weapon provide an alluring target for terrorismFact: date=October 2008.

Airport security provides defense by attempting to stop would-be attackers from bringing weapons or bombs into the airport. If they can succeed in this, then the chances of these devices getting on to aircraft are greatly reduced. As such, airport security serves two purposes: To protect the airport from attacks and crime and to protect the aircraft from attack.

Monte R. Belger of the U.S. Federal Aviation Administration notes "The goal of aviation security is to prevent harm to aircraft, passengers, and crew, as well as support national security and counter-terrorism policy."

Airport enforcement authority

While some countries may have uniform protection at all of their airports, in other countries like the United States, the protection is controlled at the state or local level. The primary personnel will vary and can include:

• A police force hired and dedicated to the airport
• A branch (substation) of the local police department stationed at the airport
• Members of the local police department assigned to the airport as their normal patrol area
• Members of a country's military
• Members of a country's airport protection service
• Police dog services for explosive detection, drug detection and other purposes

Other resources may include:

• Security guards
• Paramilitary forces
• Military forces

Process and equipment

Some tragedies have been the result of travelers being permitted to carry either weapons or items that could be used as weapons on board aircraft so that they could hijack the plane. Travelers are quickly screened by a metal detector. More advanced explosive detection machines are being used in screening such as X-ray machines. Explosive detection machines can also be used for both carry on and checked baggage. These detect volatile compounds given off from explosives using gas chromatography . A recent development is the use of backscatter X-ray scanners to detect hidden weapons and explosives on passengers. These devices, which use Compton scattering, require that the passenger stand close to a flat panel and produce a high resolution image .

Generally people are screened through airport security into the concourses, where the exit gates to the aircraft are located. This area is often called a secure or sterile area, and is referred to as airside. Passengers are discharged from airliners into the sterile area so that they usually will not have to be re-screened if disembarking from a domestic flight; however they are still subject to search at any time. Eating establishments have started using plastic glasses and utensils as opposed to glasses made out of glass and utensils made out of metal to reduce the usefulness of such items as weapons.