Security is being tightened at European and Middle East airports operating direct flights into the United States, following what is believed to be a "credible threat" from Syrian and Yemen-based al-Qaeda affiliates with access to European passports, bomb-making skills and new explosive technologies.
The nature of the threat to passenger aircraft has evolved greatly over the past 80 years. The 1940s and 1950s were host to a spate of hijackings, with the first in-flight detonation of an explosive device on a British passenger aircraft taking place in 1950.
Since that time, attacks involving explosive devices on passenger aircraft have moved from a focus on placing timer or barometric-based improvised explosive devices (IEDs) in checked luggage, towards artfully concealed passenger-borne IEDs such as Richard Reid's shoe bomb (2001), and the more recent ink cartridge bomb found on a cargo plane in 2010.
Additionally, plans to detonate liquid explosives on transatlantic flights were foiled before they came to fruition in 2006. These changes in the method of delivery and the ever-evolving technological components of terrorist IEDs are a direct result of improvements in aviation security technologies, processes and procedures.
Effective aviation security approaches have motivated terrorists to move their focus away from the placement of IEDs in unaccompanied luggage towards the use of passenger-carried explosive devices, the use of the aircraft as an explosive device itself (e.g. 9/11 attacks in the USA), and back again, towards concealing IEDs placed within the aircraft hold. Recent reports about heightened security at European and Middle East airports suggest that the threat of terrorist-borne IEDs is also evolving to include surgically implanted, non-metallic explosive materials, as well as undetectable materials concealed within laptops, mobile phones and other devices.
Picking up subtle signs
Similarly, effective aviation security approaches have motivated aviation security practitioners to change their tactics and modes of delivery. A growing reliance on pre-flight passenger screening and the use of a variety of scanning technologies and, in some instances, biometrics at the airports themselves, has resulted in a decrease in face-to-face interactions between passenger and employee as travellers move through airports.
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Perhaps it is time for aviation security managers to revisit past human behaviour-based strategies once believed to be effective, in order to combine them with modern, technologically driven approaches to ensuring passenger safety.
Specifically, the human element of surveillance can be as important as the sophisticated new scanners and technologies when it comes to picking up more subtle forms of human behaviour.
When terrorists' IEDs evolve to a point where our scanning technologies struggle to identify them, face-to-face human contact can influence the way individuals react to the airport environment. Well-trained airport personnel are more likely to pick up on signs and signals of distress, or ill-intent during periods of face-to-face contact.
For example, aviation security practitioners at Israel's Ben Gurion airport are often recognised for the effectiveness of their human factors approach to airport security. They use a combination of security technologies and face-to-face passenger interviews to ensure the security of their flights.
Missing important opportunities
Opportunities for face-to-face contact are rare in many modern airports. A passenger can check in online and quickly drop a bag off if they are checking luggage in, or walk straight through to security if they are not. Some airlines, such as EasyJet and Ryanair have abolished check-in desks, altogether, with Ryanair charging a substantial fee if passengers fail to print their boarding passes prior to their arrival at the airport.
When engagement does take place, instead of using highly trained security staff, bags and passengers are often checked in by the very same flight attendants who will look after them on the flight. As a result, this heavy reliance on online check-ins and scanning technologies, combined with the removal of frontline airport staff has the potential to make airport security more vulnerable. A lack of face-to-face contact means that we risk missing important opportunities to gauge an individual's intention or mood. Technology, no matter how good, cannot be 100 percent effective in a dynamic, public environment such as an airport.
The challenge for security practitioners to keep up with evolutions in terrorist weaponisation is ongoing. Terrorist groups will continue to view bringing down a plane as the ultimate prize. If the attackers succeed - it will be spectacular for them and have a direct impact on public perceptions of the threat, trust in government and travel behaviour. Security practitioners must use the entire suite of tools at their disposal, resulting in a healthy combination of behavioural observation, technological screening and scanning.
Failure to focus on the human element throughout the passenger process has the potential to undermine the effective preventative work taking place during the pre-flight check-in and physical airport security processes. All of these approaches must, of course, be couched within terms of civil liberties and human rights and grounded in the reality of balancing budgets for equipment, personnel and maintaining processes and procedures conducive to an acceptable passenger experience. The aviation industry and authorities face a significant challenge, not just in countering potential attacks but in not allowing travel to be adversely affected by their security procedures.
Brooke Rogers is a social psychologist and is a Reader in Risk and Terror in the Department of War Studies at King's College London where she co-directs the MA in Terrorism, Security and Society.
Follow her on Twitter: @DrBrookeRogers
The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.