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.

Obama set to tighten air security

US President Barack Obama is set to announce tightened airline security, after his officials update him on reviews prompted by a plane bomb plot.

Reviews of airport screening and of the US watch-list system were ordered after a Nigerian man known to US officials allegedly got on a plane with a device.

He tried to blow up the plane on 25 December as it prepared to land in the US city of Detroit, investigators say.

It has prompted changes to airport screening around the world.

Fourteen countries, including Nigeria, Somalia and Yemen, have been singled out by Washington for enhanced security measures for travellers.

On Tuesday at the White House, President Obama is expected to outline steps to improve watch-lists and deter future attacks, after his meeting with about 20 security and intelligence officials.

Prosecution investigation

Secretary of State Hillary Clinton, Defence Secretary Robert Gates, Homeland Security Secretary Janet Napolitano, CIA Director Leon Panetta and FBI Director Robert Mueller are among those expected at the meeting, the Associated Press news agency reported.

Mr Obama will be updated on the investigation focusing on Umar Farouk Abdulmutallab, the 23-year-old Nigerian who remains in custody, charged with attempting to destroy a plane.

Mr Abdulmutallab began his journey in Lagos, Nigeria, and changed planes at Schiphol airport in Amsterdam, the Netherlands.

His name was in a US database of about 550,000 suspected terrorists, but was not on a list that would have subjected him to additional security screening or kept him from boarding the flight.

Since the incident, officials have moved dozens of names on to "watch-" and "no-fly" lists, as they seek to overhaul security, White House spokesman Bill Burton said earlier.

Watch-list update

Those on the watch-list are subject to extra security checks, while those on the no-fly list are not allowed to board flights to the US.

Yemen-based al-Qaeda in the Arabian Peninsula said last week it had trained and equipped Mr Abdulmutallab for the plane plot.

The US re-opened its embassy in Yemen on Tuesday, following what it called successful counter-terrorism operations by government security forces on Monday north of the capital.

A BBC correspondent in the Yemeni capital Sanaa says the embassy was referring to a strike that reportedly killed two al-Qaeda operatives.

The embassy had closed on Sunday in response to what it said were al-Qaeda threats. The British and French embassies have resumed operations, but remain closed to the public.

Yemeni authorities have tightened security measures at Sanaa's airport, as well as around several other embassies.

Jet bomb suspect's journey 'began in Ghana'

The Nigerian man accused of trying to blow up a transatlantic airline on Christmas Day began his journey in Ghana, the Nigerian authorities say.

Umar Farouk Abdulmutallab spent just half an hour at the airport in Lagos before transferring to an Amsterdam flight, the information minister said.

It had been assumed the 23-year-old began his journey in Nigeria.

But Ghana has disputed Nigeria's timings, saying Mr Abdulmutallab's stop-over was at least three hours.

A senior Ghanaian government official told the BBC that the suspect bought a one-way ticket to Lagos from Accra that would have given him more than three hours at the airport.

He accused the Nigerians of attempting to "pass the buck" as the search for security lapses continues, the BBC's West Africa Correspondent Caspar Leighton reports from Accra.

Nigeria's Information Minister Dora Akunyili earlier told the BBC that it was now known Mr Abdulmutallab had boarded a Virgin Nigeria plane from Accra to Nigeria, arriving at Lagos' Murtala Muhammed airport on 24 December.

His passport was scanned on entry into Nigeria at 2008 (1908GMT), and again, as he boarded the flight to Amsterdam, at 2035, she said.

"He was able to connect that fast because he was not checking in any luggage," she said.

From Amsterdam, the Northwest Airlines Flight 253 - with 278 passengers and 11 crew aboard - went on to the US city of Detroit.

Some 20 minutes before landing at the city's Metropolitan Airport, on the afternoon of Christmas Day, Mr Abdulmutallab was spotted by flight crew and passengers trying to ignite explosives strapped to his leg, investigators say.

The explosives failed to detonate, although it is thought they may have caused a small fire which burned the suspect's leg.

He is now in US custody.

Body scanners

The incident has led to a worldwide re-think about security procedures.

US President Barack Obama is reading reports received about the security lapses that led to the near-disaster in Detroit, and intends to meet security chiefs on Tuesday to discuss new measures.

British Prime Minister Gordon Brown announced on Friday he had ordered a review of existing security measures, and would "move quickly" to enhance airport security.

Full-body scanners would be among the new technologies considered, he said.

The Dutch authorities announced earlier this week that body scanners would be used on all passengers flying from Amsterdam's Schiphol airport to the US.

Shebab 'help'

The incident has also thrown the spotlight on Yemen, where Mr Abdulmutallab was living in the months leading up to the attack.

It is feared the troubled country is becoming a major training centre for militants, with several hundred al-Qaeda members believed to be operating there.

In recent weeks, Yemen has launched major operations against al-Qaeda with US backing, but has warned that it needs more Western support to tackle the threat.

Britain's prime minister has called a summit in London to discuss radicalisation in Yemen.

Mr Brown's office said the 28 January event had support from Washington and the European Union, and Mr Brown aimed to attract Saudi Arabia and Gulf states.

Somalia's hardline Shabab group - which controls large swathes of Somalia, including much of the capital Mogadishu - said on Friday it would send fighters to help fellow militants in Yemen.

"We tell our Muslim brothers in Yemen that we will cross the water between us and reach your place to assist you fight the enemy of Allah," said Shebab's Sheikh Mukhtar Robow Abu Mansour.

Obama orders air security review after jet bomb attempt

US President Barack Obama has ordered a review of air security measures after a Nigerian man allegedly tried to blow up a trans-Atlantic jet on Christmas Day.

Spokesman Robert Gibbs said the president wanted to know how a man carrying dangerous substance PETN had managed to board a flight in Amsterdam.

He said the system of watch-lists would also be examined after it emerged the man was listed and known to officials.

A US record for 23-year-old Umar Farouk Abdulmutallab was created last month.

Mr Gibbs told ABC News that the review would examine, firstly, the system of watch-lists used by government agencies, which includes three lists which become progressively shorter as risk increases.

'Dangerous substance'

The lists include a watch-list, with some 550,000 names on it, a "selectee" list with 18,000 people within the higher-risk category, and a "no-fly" list with 4,000 names of people who are not permitted to board planes.

Mr Abdulmutallab was placed on the lowest-risk list by US authorities in November 2009, after his father alerted authorities about the behaviour of his son.

Mr Gibbs said the number of people on the watch-list was "a huge number".

"The president has asked that a review be undertaken to ensure that any information gets to where it needs to go, to the people making the decisions. The president wants to review some of these procedures and see if they need to be updated," he said.

On 24 December Mr Abdulmutallab travelled from Nigeria to Amsterdam and then on to Detroit with an explosive device attached to his body, US officials say.

Shortly before the flight was due to land in the US, he allegedly attempted to detonate the device beneath a blanket but he was overpowered by passengers and crew.

Mr Abdulmutallab, the son of a prominent Nigerian banker, has been charged by US authorities with trying to blow up the Northwest Airlines flight as it was coming in to land.

US airlines especially have tightened security after the attempt, increasing screenings and body searches and, in some cases, confining passengers to their seats without pillows or blankets for the last hour of their flight.

Mitigation measures

Mr Gibbs said "air detection capabilities" would also be examined as part of the review.

"The president has asked the Department of Homeland Security to answer the - quite frankly - the very real question about how somebody with something as dangerous as PETN could have gotten onto a plane in Amsterdam."

PETN, or pentaerythritol, is the same material used by convicted shoe bomber Richard Reid who tried to destroy a trans-Atlantic flight in 2001.

Mr Abdulmutallab's route originally began in Yemen, from where he travelled to Ethiopia, then to Ghana and finally Nigeria.

According to Nigeria's information minister, Mr Abdulmutallab had arrived and flown out of Nigeria in the space of a single day.

"The man in question has been living outside the country for a while," said Dora Akunyili.

"He sneaked into Nigeria on the 24th of December and left the same day."

Nigerian authorities, who on Sunday pledged to co-operate fully with the US investigation, said screening would be enforced for all passengers passing through the country's 22 airports.

Wealthy or influential people and their families are often allowed to skip checks, media reports say.

Speaking to ABC News, Homeland Security Secretary Janet Napolitano said there was no immediate indication that Mr Abdulmutallab was part of a broader terror plot.

"Right now we have no indication that it is part of anything larger. But obviously the investigation continues. And we have instituted more screening and what we call mitigation measures at airports," she said.