Airport security
Airport security consists of techniques and methods used in protecting airports from crime and terrorism. Most large airports have their own police force backed up by security guards. In some countries and during wars, paramilitary forces or even soldiers protect airports from internal and external threats.
Large numbers of people pass through an airport every day. Such a large gathering of persons presents in itself a natural target for terrorism due to the number of people crowded into a small area.
Travelers must not be allowed to carry weapons aboard aircraft in order to prevent a aircraft hijacking. Therefore, travelers must be quickly but efficiently searched. Baggage must be screened to prevent the carrying of bombs aboard an aircraft. X-ray machines are often used to speed this process.
The world's worst failure of airport security was the September 11th attack on the World Trade Center and The Pentagon using hijacked jetliners.
Airport security in the United States is now provided by the Transportation Security Administration of the Department of Homeland Security. Prior to September 11th airport security was provided by security guard companies, often by the lowest bidder due to pressure from airport operators and airlines. It was not uncommon that the lowest-paid employee in the airport was a security guard.