Would you trust the human eye to spot a bomb?

Airline passengers will undergo full body scans as security measures are stepped up after the alleged plan to blow up a plane on Christmas Day. But the technology is only ever as good as the people who operate it, says Chris Yates.

Security measures for British air passengers are about to get a lot more stringent.

After the alleged attempt to bomb a transatlantic passenger plane over the US on Christmas Day, full body scanners in major British airports have been given the go-ahead.

In addition to these "naked" imaging scanners, there will be a greater reliance on explosive residue detectors and a full scale review of the security system that exists in this country.

Full body scanners, or whole body imaging (WMI), as the technology is known in the trade, will allow airport security staff to see beneath passenger clothing to ensure travelers are not carrying concealed weapons of most types.

The equipment has been around for some time, with a current trial at Manchester airport, but until now plans to roll it out have been held back by concerns about privacy. The scanners effectively render a naked image of each passenger - highlighting any objects stored close to the body as well as more intimate details.

Yet the fact such concerns have been swiftly swept aside in the immediate aftermath of the Christmas Day scare is evidence of how international air travellers are about to witness another tightening of the security net.

But how effective are these full body scanners and are we relying on them too heavily?

Regardless of whether Whole Body Imaging (WMI) could have identified the explosive device allegedly used in the failed Christmas Day attack, this type of technology in the airport environment is a potential game changer for the safety of air passengers. It also gives security personnel much needed additional capability.

Human error

But it cannot be seen as the panacea to the threats we face today.

Full body scanners are often only as good as the people paid to be behind the screens, analysing the succession of complex images scrolling in front of their eyes.

Staff monitoring screens typically only do so for a two-hour stretch - one of a rotation of duties to stop them from getting bored.

But even then, they are only human and it's a human frailty that when attention is focused on a mundane task, it can easily wander - distracted by the sight of an attractive man or woman or a passing celebrity.

There are moves at the moment to relocate the operatives looking at screens to a remote area - a darkened room where there are no distractions. It's one of the ways that the security industry is looking at improving scanning and minimising human error.

So maybe the alternative is to go for something that minimises, even sidesteps, human error. entirely. With some emerging technologies, such as liquid detectors, the machines themselves make the call.

Given that the alleged Christmas Day plot is said to have relied on liquid for the in-flight bomb, there is clearly a case for liquid detectors at airports sooner rather than later.

The hardware and software is already available.

Green light scanner

A bottle scanner device has undergone pilot trials at Newcastle Airport and is being assessed by Manchester airport.

The scanner is an ingenious piece of kit - a standalone system providing a highly accurate means to positively verify whether the content of a bottle is safe for carriage in the passenger cabin or otherwise. It literally gives a green light for "OK" or a red light.

Or there is a piece of technology which can be used with existing baggage X-ray systems to detect liquid explosives and chemical threats in real time, for a fraction of the cost of deploying new hardware.

Gordon Brown has also signalled that passengers could see greater use of explosive residue detection systems that are already deployed at UK airports for random screening of passenger belongings.

Many of us are familiar with having items of hand luggage swabbed and analysed by these labour intensive devices at airports. However, this method of detection is evolving dramatically.

An explosive residue detection system developed by Loughborough University and presently being commercialised can remotely scan crowded areas, such as airports and train stations, automatically alerting an operator if it detects traces of explosives.

A hand-held variant of the system is also under development and is ideally suited to deployment in the central screening areas within airports.

PR exercise?

Of course, it could be pointed out that for all the money and time spent on elaborate scanning equipment, as far as I know, they have yet to be instrumental in foiling a terrorist plot.

Indeed, many people will say that scanning at airports is nothing but a PR exercise - there to reassure the overwhelming majority of law-abiding passengers while also acting as a deterrent for violent fanatics.

That could perhaps have been said of the old style X-ray scanners. But the level of sophistication we have nowadays gives much greater capability to detect weapons.

Yet security at airports is as much about technique as technology. The technique involves, amongst other things, passenger profiling. Rudimentary forms of profiling have been commonplace at airports for very many years and we're all used to the sort of basic questions asked of us prior to and during the check in process.

Traditionally, the UK has shied away from full on profiling of the kind passengers travelling to Israel might undergo for example. However, there is now a strong case for much greater use of this technique at airports.

Civil liberties groups have long been opposed to passenger profiling, citing issues surrounding whether individuals might be profiled on grounds of ethnic background and so forth. There is though no reason why greater profiling cannot be conducted without recourse to contentious issues such as race and religion.

The aviation industry routinely collects vast amounts of data on our travelling habits that can be used to build up an extremely useful profile. Information regarding the destination, frequency and duration of overseas trips allows those tasked with ensuring the security of flights to positively identify passengers who may travel to regions of the world determined to be high-risk for example. That enables higher levels of security to be applied to that person as he or she passes through the airport.

What is required is a system of systems comprising both technique and technology. The technique must include greater use of passenger profiling whilst the technology must include advanced tools giving greater detection capability.

Such techniques, when combined with greater use of advanced technologies, give us much greater detection capability on the frontline at our airports.

Chris Yates is an aviation security analyst with Jane's Information Group.