Soft Target Security: Environmental design and the deterrence of terrorist attacks on soft targets in aviation transportation

Linda JAshari


Terrorist attacks on soft targets at airports have increased in the last decade. The events of September 11, 2001 exposed deep vulnerabilities in the security of the aviation sector. As a result, the U.S. government enacted concrete policies and procedures to prevent future airline hijackings and to deter prohibited items from entering aircraft. However, since 2011, 14 airport attacks have occurred worldwide.[1] The increase in attacks at airports demonstrates that adversaries are continuously seeking new targets in the aviation sector. At the same time, a general increase in air travel has led to larger crowds at airports. An attack on soft targets in the airport environment could cause a significant disruption of the aviation industry, leading to a large negative effect on the U.S. economy, not to mention the social and psychological health of this nation’s citizens.

An examination of several airports reveals that ticket counters, baggage claim areas, and screening checkpoint queues are easily accessible to adversaries seeking to harm this country. Such areas are open to the general public, including nefarious actors engaged in pre-surveillance to establish a plan of attack. Presently, people have minimal physical protection in these publicly accessible areas. Furthermore, the United States does not have a systematic national policy approach in place for airport soft target security (STS). The purpose of this thesis is to explore how policy approaches and environmental design countermeasures can be applied to the problem of soft target protection in airports. The overarching goal is to mitigate the threat to crowds, minimize the impact of an attack, and disrupt the terrorist planning process.

The recent increase of airport attacks across the globe and the limited literature for explicitly protecting crowds in the airport environment provide the impetus for this research. The Aviation and Transportation Security Act (ATSA) does not specifically mandate the protection of public spaces within the airport environment. The death of 32 civilians during the terrorist attack at Brussels International Airport, for example, illustrates the vulnerability of crowds in these spaces. However, empirical research in the criminology field, such as crime prevention through environmental design (CPTED), offers proven methods that may be transferred to the airport construct. Based on this framework, this research explores methods of deterring adversaries, disrupting the terrorist planning cycle, and prescribing proven environmental counter-measures to mitigate an attack on soft targets in airports.

The research design and solution included three case studies of terrorist attacks on soft targets in airports: Brussels in 2017, Los Angeles in 2013, and Glasgow in 2007. These cases were chosen because they were deliberate attacks on soft targets in airports. The Brussels case involved the use of improvised explosive devices (IEDs) hidden in luggage and detonated by terrorists in the interior public terminal. The Los Angeles case involved the use of an assault rifle by an active shooter on both the non-sterile and sterile area, and the Glasgow case involved the use of a vehicle borne improvised explosive devices (VBIEDs) to attack a public terminal.

Human perception of target selection, airport configuration, attack consequences on security, the economy, and implications of airport design were analyzed. The data sources derived from literature, agency reports, airport records, and configuration diagrams. The analysis criteria included airport terminal layouts, infrastructure materials, and event documentation. The mode of analysis included attack location, method, and impact. The independent variable was the airport environmental design and the dependent variable was human attack perception. The United States and European Union (EU) soft target counter-terrorism strategies were also compared and analyzed.

Aviation transportation is critical to the lives of Americans and the global economy. Aviation alone accounts for more than 5% of U.S. gross domestic product (GDP) contributing over $1.6 trillion to the total market economy.[2] An airport attack could result in a loss of $17 billion in GDP from lost air travel.[3] As demonstrated by the case studies, airport attacks disrupt the aviation system network and cause cascading effects. The attacks cost airports and airlines millions of dollars in lost airline revenues, business continuity operations, emergency response, infrastructure damage/renovation, crowd management, injuries, and deaths. The attacks also impact both the local and national economy. In Brussels for example, the attack cost the Belgian economy an estimated four billion euros.[4] To evolve with the emerging threat, a national systematic approach is needed to address the protection of crowds in the airport environment.

In the case of Brussels where terrorist used improvised explosives, the materials used throughout the interior directly added to the human casualty rate. People were injured by building debris, glass windows, and interior ceiling panels fragmented by the explosives’ shock wave. In the Glasgow case, the terrorist’s attempt to detonate the explosives by setting a fire resulted in damage to the exterior and interior building that caused extensive smoke in the interior building, and water damage from automatic sprinkler systems. In Los Angeles, the spontaneous evacuation of over 4,500 people, the confinement of an addition 20,000 people in the terminals, and the impact to 1,500 flights, resulted in a significant disruption of airport operations.

This research revealed that alternative methods for airport environmental design exist and can be used effectively to mitigate risk. Airport authorities and government officials made some significant changes to protect soft targets and improved airport infrastructure in the aftermath of the attacks. For example, at Brussels and Glasgow airports, passenger pick-up and drop-off zones were moved outside the perimeter of the terminal building. Additionally, blast mitigation materials replaced glass fixtures. Turnstiles have been added to the entrance of security screening checkpoints and baggage claim areas as extra layers of access control security. Additionally at Glasgow airport, 300 steel bollards and automatic number plate recognizers (ANPR) were installed. Los Angeles airport is continuing to develop environmental counter-measures, and plans are underway to add security desks in the public terminal areas.

This thesis makes several recommendations to implement airport environmental counter-measures that will improve STS, specifically in airline ticketing queues, screening checkpoint queues, and baggage claim areas. These spaces are critical pinch-points that concentrate soft targets into high density targets of opportunity. The recommendations include applying the CPTED principles of defensible space (territoriality, surveillance, maintenance, and access control) by using the design concepts of organized, mechanical, and natural features. These concepts include altering the adversaries’ human reactional elements and perception of targets. Modifying temperature, pressure, lighting, sound, and creating optical illusions can achieve these measures. Placing camouflage elements, such as fabric netting, mirrors, indoor planters, and water features, provide deterrence and deception in perception capabilities of crowds. Additionally, adding sound absorbing materials decreases the noise level and makes the crowd appear smaller while simultaneously calming the users of the space.

In the airline ticketing area, crowd congestion can be minimized and distributed by increasing the use of technology. For example, technology developed to have passenger pre-pay for weighing and checking in luggage (pre-airport arrival) can significantly decrease airline check-in queues. Establishing multiple drop-off zones for luggage dispersed throughout the airport grounds further reduces crowd formations. Additionally, bomb-sniffing canines should be actively utilized in these areas to detect explosives and provide a deterrence effect. Shrapnel and fragmentation resistant materials should be utilized throughout these areas to mitigate the risk from IED explosions.

In the screening checkpoint queue, distributed versus centralized queue concepts offer enhanced threat reduction at minimal cost. Distributed queuing also decreases the number of individuals per square foot, which makes the crowd appear smaller. Blocking the view of the queuing line with large planters, artwork panels, or frosted blast-resistant glass can further deter the adversary from conducting pre-surveillance or seeing the “big picture.” Additionally, the use of lighting, such as in theater production, can alter the perception of the line.

Similar features can also be integrated in the baggage claim areas to obstruct the view of attackers and provide mitigation elements to protect people. In the event of an IED explosion or active shooter, these materials can improve shock and projectile absorption. The placement of closed circuit televisions (CCTVs), explosive-detection canines, and additional police patrols in these areas add additional layers of security. Lastly, placing the baggage claim in an inaccessible area to the public, or installing turnstiles to limit access, decreases the risk of opportunistic attacks.

This thesis also recommends the utilization of risk assessment models, physical structures and technology, robotics, and simulation models to evaluate and enhance security measures properly in the non-sterile airport domain. Independent risk assessment groups, such as the UK’s model of the Risk Advisory Group (RAG) and Security Executive Group (SEG), can provide subject matter expertise to assess attack methodology through a game theory model. The deliberative method for ranking risks is also a great tool to calculate the number of lives lost per event. Physical blast-resistant technology, such as Kalwall windowpanes, offer effective alternatives for airport glass re-placement because they are shatterproof, fire-retardant, lightweight, and aesthetically appealing. Portable bulletproof and blast-resistant curtains, such as origami Kevlar shields, deliver an adaptable method to the evolving threat, are flexible, lightweight, and can be transported. Robots, such as Knightscope, offer the ability to augment physical security techniques because they have advanced detection sensors, such as audio and visual recognition, thermal imaging, license plate recognition, weapon detection, emergency alert alarms, and can transmit pre-recorded announcements, which are effective for crowd management. Computerized simulation models provide a great alternative to attack scenario planning and minimize costs needed to assess and implement physical security counter-measures. The Multi-Agent System, for example, is effectively used for emergency management and evacuation simulations. The Anti-Terror Risk Infrastructure Protection Model (ATRiM) also offers an analysis of operational and physical risk vulnerabilities in infrastructure.

Policies, such as UK’s Countering Terrorism (CONTEST), which place crowd protection in the fore of government planning and risk mitigation strategies, offer best practices to emulate. In the United States, the Transportation Security Administration has made significant strides in risk-based security. Over the years, it has updated policies to detect and deter threats, deployed explosive detection canine handlers and visible intermodal prevention and response teams, and liaised with the international aviation community to enhance aviation transportation security. Ultimately, however, it is up to airport operators and the airline industry to protect the masses in the airport critical infrastructure. The challenge still remains of how to protect soft targets collectively.

Establishing policies and environmental counter-measures to be people-centric provides this opportunity. The environmental elements of CPTED provide strategic methods for crowd-protection and can fill the gap of physically securing the soft targets. If applied strategically, these features can minimize threat impact, afford resiliency, and boost continuity of operations. A systematic approach to STS can save billions of dollars for the aviation industry, airport infrastructure, commerce, and the U.S. economy. As passenger numbers continue to increase in airports worldwide, it is imperative to take a proactive stance to mitigate the risk of attacks on innocent civilians.



[1] “Recent Airport Attacks at a Glance,” Associated Press, June 29, 2016,
bb7e944c6b3bc8045b39bd24e. This article does not include the Florida Fort Lauderdale active shooter event on January 6, 2017.

[2] Federal Aviation Administration, The Economic Impact of Civil Aviation on the U.S. Economy (Washington, DC: Federal Aviation Administration, 2016),

[3] Emily Gersema, “Attack on an Airline or Airport Could Cost the Economy Billions in Losses,” USC News, paragraphs 8, 9, February 9, 2017,

[4] Damien Sharkov, “Brussels Attacks to Cost Belgium $4.47 Billion,” Newsweek, March 23, 2016,

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