When, on Christmas Day 2009, a 23-year-old Nigerian national attempted to blow up a transatlantic jet bound for Detroit, post-9/11 passenger safety concerns around airports were once again revived to a dramatic degree.

Umar Farouk Abdulmutallab, who had concealed the plastic explosives in his underwear, had embarked from Lagos on Christmas Eve before changing planes at Amsterdam Airport Schiphol. Being a transit passenger, he had not undergone any surveillance.

At the time, Schiphol’s passenger scanners – first implemented on a large scale in 2007 – were only used for European flights. The fallout from the incident was immediate; only a matter of days later, Dutch airport authorities, alongside the Dutch national coordinator for counterterrorism, began lobbying the European Commission to make passenger scanners mandatory on the continent.

Not only were authorities forced to review the issue of maintaining tight security and vigilance at airports, it had to be done without compromising passengers’ health and privacy. The EU was pressed into benchmarking the different types of scanners on the market: namely, X-ray backscatter technology and millimetre-wave machines.

Banning backscatter technology

Two years later, in 2011, these deliberations led to backscatter machines being banned at European airports, a move sanctioned by the EU’s 27 member nations. More penetrative than millimetre-wave scanners through the use of ionised radiation – enough, in theory, to damage DNA and pose a cancer risk – health and safety concerns were cited as the primary reason for the mandate.

At the beginning of this year, the US, which had hitherto employed amix of backscatter and millimetre-wave scanners, followed suit, with the Transport Security Administration announcing plans to completely remove the former technology from airports, forcing some hubs to temporarily revert back to using metal detectors.

"Regulations on aviation security have obviously changed widely in the wake of 9/11," explains Bart Mos, senior security officer at Schiphol. "Before that time, all an airport needed was approval from authorities on a national level, which meant screening, most of the time, constituted simply walking through a metal detector, or frisking. It wasn’t good enough.

"Today’s millimetre-wave scanners use automated target recognition software (ATR), which displays a generic ‘stickman’ image instead of showing full human body detail."

"With the backscatter, although the levels of radiation used are miniscule – smaller than that found with a mobile phone – it was enough to convince the European Parliament to issue the ruling we have now. So at Schiphol, we then took a gamble and bought millimetre-wave machines; in hindsight it was the right decision."

Subsequently, a general consensus has emerged that millimetre-wave scanners are the best alternative for airports that are looking to tighten security. Deployed at Schiphol’s security and customs controls, Mos, who describes the technology as "harmless", claims it has both allayed passengers’ health fears and engendered faster traffic.

"The scanning of each passenger now takes an average of eight seconds," he says. "If there is any kind of alarm, it will be signalled on the screen, which the passenger can see and then solve themselves, so to speak. It doesn’t require a full-body pat-down, so that cuts downs on time, too. That was really the rationale behind this type of screening – it’s more passenger-friendly."

So the feedback has been positive? "People like it," confirms Mos. "No one really asked any questions when we first rolled it out either. I think old-fashioned walk-through metal detectors became so unpopular with passengers. There were often complaints over harassment, so this new technology is being embraced as a hassle-free alternative."

The benefits of ATR software

The need to safeguard passenger privacy has also been thrown into sharp relief, meaning the lack of invasiveness afforded by millimetre-wave scanners makes them particularly attractive. For some time, watchdogs have voiced concerns over how much of the body should be viewed by airport staff, with many labelling backscatters – able to produce naked images – as nothing more than a kind of digital strip search.

Today’s millimetre-wave scanners, as found at Schiphol, use automated target recognition software (ATR), which displays a generic ‘stickman’ image – bearing no discernible, lifelike correlation to the passenger – instead of showing full human body detail.

"The European Parliament has long been concerned with the issue of privacy," explains Mos. "For example, when airports first started using scanners, the screeners were situated remotely from the equipment, which a lot of people didn’t like. But today, there are no images of the passenger, just a generic outline."

"If there is any kind of alarm, it will be signalled on the screen, which the passenger can see and then solve themselves."

In the past, there were also accusations over airports warehousing images for future reference. That’s not the case anymore, says Mos – "while it could be implemented in a test environment or the laboratory, no images can be retained at all. Besides, there is no image of the passenger anymore".

Regulations are also becoming more stringent. Today, it is common practice for EU inspectorates to turn up at airports unannounced and vet security procedures. Schiphol has no plans to rest on its laurels, either – it is currently working alongside L-3 Communications, the US-based supplier of command and control, communications, intelligence, surveillance and reconnaissance systems, to update its current technology.

"We are already testing a new system, which we are looking to roll out at one of our checkpoints in the coming months," says Mos. "It is smaller – almost one millimetre less with the dual lane – and has a smaller footprint with a shorter scanning time of six seconds instead of eight. It is really about improving the software these days, as it is the software that is improving the machines, not the hardware."

Trace detection methods

While millimetre-wave technology is clearly here to stay, airports still need to retain contingency security methods, meaning traditional pat-downs haven’t been consigned to the past just yet. Trace detection machines – more commonly known as puffer machines – will also continue to play a major part in detecting explosives and drugs at airports, albeit to complement rather than replace existing machines.

"Trace detection has also become important, particularly on higher-risk flights," says Mos. "So we are looking to add this to our existing equipment, including shoe-scanning devices. These are the improvements I see for the forthcoming years."

Mos is loath to use the term ‘full-body scan’, which he believes is construed as too clinical by passengers – "it sounds like you are in a hospital. At Schiphol, we prefer to use the term security scan."

Semantics aside, Schiphol’s role as a torchbearer in the field is very much defined by its ongoing practical efforts and making use of technology that is both watertight and passenger-friendly.