Practice Profile: Metal Detectors and Security Screenings at Airports as a Counterterrorism Strategy

Counterterrorism includes strategies, policies, practices, interventions, or tactics that are designed to prevent or respond to terrorism. Target hardening at airports is an example of a defensive counterterrorism intervention that is designed to increase the detection of potential terrorism by placing metal detectors in airports and increasing security screening of passengers before they board planes. This practice is rated Promising for significantly reducing events of airplane hijackings.

Practice Goals/Practice Components

Counterterrorism includes strategies, policies, practices, interventions, or tactics that are designed to prevent or respond to acts of terrorism. There are a number of definitions of terrorism that attempt to differentiate terrorism from other violent crimes or acts of violence. Unfortunately, there is no universal, agreed-upon definition. Terrorism, as defined by the Federal Bureau of Investigation (FBI), is the “unlawful use of force or violence against persons or property to intimidate or coerce a government, the civilian population, or any segment thereof, in furtherance of political or social objectives” (NIJ 2011). The FBI definition focuses on methods of terrorism, rather than motivation of the terrorist, and differentiates between international terrorism and domestic terrorism. Regardless of the specific definition, violence is an important component of terrorism, and can take on many forms such as kidnappings, bombings, or hijackings of planes (Sandler 2011).

Counterterrorism can take on many forms, such as defensive and proactive measures; prevention, detection, and management strategies; and law enforcement responses. Specific examples of counterterrorism strategies, tactics, and tools include (but are not limited to) buildings security, CCTV, distribution of no-fly lists, weapons detection devices, diplomatic efforts, educational programs, emergency preparedness, foreign aid, fortification of embassies, gas mask distribution, hostage negotiation, legislation, military interventions, multilateral agreements, psychological counseling, seal-/tamper-proof devices, and situational crime prevention (Sandler 2011; Lum, Kennedy, and Sherley 2006b).

Target hardening at airports is an example of a defensive counterterrorism intervention that is designed to increase the detection of potential terrorism and deter potential terrorists. Target hardening at airports can be done by placing metal detectors at certain key locations and increasing security screening of all passengers before they board planes. Installing metal detectors and requiring security screening of passengers represent counterterrorism strategies that are visible, identifiable, and known to the public when they enter airports (Dugan, LaFree, and Piquero 2005).

Metal detectors and tighter screening of passengers were interventions implemented in airports throughout the United States beginning in the early 1970s. The measures were put into place in response to a number of domestic and international aerial hijacking events that took place in the 1960s and 1970s.

Practice Theory

The strategy of placing metal detectors at airports and increasing screening of passengers before they board planes has elements of situational crime prevention as well as those of deterrence and rational choice theory. Situational crime prevention focuses on reducing the opportunities for crime, while also increasing the perceived risk of apprehension (Clarke 1983). This can include efforts such as target hardening. Generally, the purpose of target hardening is to make physical entry more difficult or more risky.

Deterrence and rational choice theory holds that humans are rational beings who consider the consequences of their actions and are deterred from engaging in continual patterns of offending as a result of the certainty, severity, and celerity of punishment (Dugan, LaFree, and Piquero 2005). It assumes that individuals weigh the costs and benefits of crime, and therefore crime can be prevented by increasing the costs or decreasing the rewards of committing a crime. Counterterrorism strategies, such as the use of metal detectors, attempt to raise the perceived cost of committing terrorist acts, such as hijacking, by increasing the certainty of detection (Dugan, LaFree, and Piquero 2005).

Additional Information

It should be noted that studies included in the meta-analysis by Lum, Kennedy, and Sherley (2006a), which were assessed for this review, did not examine counterterrorism strategies that have been put into place at airports since 2001, as the authors could not find recent evaluation work.

Lum, Kennedy, and Sherley (2006a) also examined the effect of interventions that increased airport security on nonhijacking events, such as assassinations, bombings, hostage taking, and death. The weighted mean effect size was 6.8, meaning that an increase in airport security led to a statistically significant increase of approximately 6.8 nonhijacking events per unit of time. This may suggest that increasing security at airports had a displacement or substitution effect, leading to increases in other types of terrorism not involving airplanes. However, when the hijacking and nonhijacking terrorism events are examined together, the effect of increased airport security was not statistically significant.

These sources were used in the development of the practice profile:

These sources were used in the development of the practice profile:

Clarke, Ronald V. 1983. “Situational Crime Prevention: Its Theoretical Basis and Practice Scope.” Crime and Justice 4:225–56.

Dugan, Laura, Gary LaFree, and Alex R. Piquero. 2005. “Testing a Rational Choice Model of Airline Hijackings.” Criminology 43(4):1031–65.

Lum, Cynthia, Leslie W. Kennedy, and Alison J. Sherley. 2006b. “Are Counter-Terrorism Strategies Effective? The Results of the Campbell Systematic Review on Counter-Terrorism Evaluation Research.” Journal of Experimental Criminology 2:489–516.

Lum, Cynthia, Leslie W. Kennedy, and Alison J. Sherley. 2008. “Is Counter-Terrorism Policy Evidence-Based? What Works, What Harms, and What is Unknown.” Psicothema 20(1):35–42.

(NIJ) National Institute of Justice. 2011. “Terrorism”. Accessed on June 19, 2015.

Sandler, Todd. 2011. “The Many Faces of Counterterrorism: An Introduction.” Public Choice 149:225–34.