Until the 1960s, airport security was relatively simple, requiring nothing more than civilian police to provide protection against conventional crimes such as theft, pickpocketing, vandalism, and breaking and entering. However, in the 1960s civil aviation became a recognized target for politically motivated crimes. These crimes came to include general acts of terrorism, such as mass shootings and bombings and, especially, aircraft hijacking.

Although the first aircraft hijacking occurred in 1931 in Peru, such events were rare, with no more than a handful each year, and generally without any political motive. However, by the late 1960s, politically motivated hijackings to Cuba had become common. In 1969, for example, there were 87 hijackings worldwide, of which 71 were related to Cuba, which typically granted political asylum to the hijackers.

The International Civil Aviation Organization (ICAO), which quickly recognized that passenger airliners had become political targets, responded in the decades of the 1960s and ’70s with three major conventions covering “unlawful acts against civil aviation.” (See also air law: International regulation.) To combat the crimes of hijacking and terrorism, the following international conventions established minimum conditions for appropriate security countermeasures to be adopted in an international context:

• Convention on Offences and Certain Other Acts Committed on Board Aircraft, commonly called the Tokyo Convention, was signed on Sept. 14, 1963, and went into force on Dec. 4, 1969—concerned with crimes on board aircraft, particularly any crime that jeopardizes the safety of the aircraft and its passengers;
• Convention for the Suppression of Unlawful Seizure of Aircraft, commonly called The Hague Convention, was signed on Dec. 16, 1970, and went into force on Oct. 14, 1971—concerned specifically with the offence of hijacking, with a recommendation that it should be made an extraditable offence for all member countries;
• Convention for the Suppression of Unlawful Acts Against the Safety of Civil Aviation, commonly called the Montreal Convention, was signed on Sept. 23, 1971, and went into force on Jan. 26, 1973—broadened the scope of The Hague Convention to include the crime of sabotage.

These conventions resulted in many ICAO recommendations for the enforcement of greater security at airports. However, because the ICAO has no national jurisdiction, the organization’s recommendations needed to be translated into individual national laws. Following the Tokyo Convention, the ICAO measures were widely adopted by most national civil aviation authorities, although the efficiency of the security procedures adopted varied greatly throughout the world. Countries that had no history of domestic civil terrorism became overconfident in their security measures, believing that only international flights were real targets for terrorist attacks. However, as terrorist acts continued to occur against passenger airliners, security measures gradually became less lax in most jurisdictions.

Initially, the principal objective of security measures was to ensure that passengers could not board aircraft with weapons or explosives. Passengers were scanned with magnetometers and suspicious individuals selected for body searches; carry-on baggage was routinely passed through X-ray machines. Public access to the aprons and operational areas was denied, except for authorized staff, as was unnecessary access to the nonpublic areas of the terminal. As control of passengers and carry-on baggage tightened, hijackings were increasingly replaced by acts of sabotage to aircraft, carried out by explosive devices secreted in baggage carried in the airplane’s hold. By the late 1990s, the ICAO had produced recommendations that all hold baggage should be screened for explosive and dangerous devices. The operational areas of civil airfields were enclosed by security fences, with manned access gates and visual surveillance of much of the areas by closed-circuit television.

In 2001, the September 11 attacks produced a sea change in much of the thinking surrounding airport security. In a period of two hours, a single terrorist organization wreaked an unprecedented level of destruction in the United States by using hijacked airliners as missiles. For the first time, civil transport aircraft, loaded with passengers and, most significantly, with a nearly full load of fuel, had been converted to destructive weapons.

Authorities responded to these hijackings with an intensification of security procedures at airports around the world. Passenger and baggage search procedures were made significantly more thorough, involving more careful screening for known terrorists (including the creation of various no-fly and watch lists of risky individuals) and potentially problematic carry-on items. Passenger terminals increased the level and sophistication of security equipment, the number of staff employed in security procedures, and the space provided for security operations. As a result, recommended check-in times for departing international passengers at many airports became as much as three hours before scheduled departure.

Hand baggage and checked baggage both became subject to strict scrutiny following Sept. 11, 2001. Many additional airports installed X-ray equipment, for spotting metal items in baggage or concealed in clothing, and massive electronic detection systems (EDS), which can detect trace molecules released by explosive materials. The massive weight of EDS equipment frequently requires structural modifications to existing buildings, and the size of the equipment often requires a reallocation of floor space. In many airports, installed security equipment now must be approved and certified by the national government.

Another problem for security at airports is the possibility of a car or truck being loaded with explosives and detonated near people or facilities. In particular, the threat from such “car bombs” forced greater caution with the location and operation of passenger pick-up areas and airport parking facilities. Parking garages that were integrated into the design of the passenger terminal pose a special danger. At those airports where parking design results in a threat to the safety of the terminal building from potential car bombs, operational procedures have been reevaluated and changed. In many cases, parking facilities integrated into the terminal itself have been closed.

The threat of terrorist attacks has meant that, for the foreseeable future and probably permanently, civil aviation cannot return to a situation of relaxed security. Eventually, access to airport terminals might require that all persons pass through some form of security check prior to check-in, that all passengers and baggage be thoroughly scrutinized for weapons and explosives, and that passengers even undergo profiling interviews to identify potential problem travelers.