Technology exists that might have detected explosives hidden in the underwear of a Nigerian man accused of trying to blow up a plane over Detroit, but cost and privacy worries have until now prevented its widespread use.

Umar Farouk Abdulmutallab, 23, is suspected of trying to ignite an explosive called PETN using a chemical-filled syringe as Northwest Flight 253 approached Detroit on Christmas morning.

He had passed through security checks in Lagos and Amsterdam, where standard metal detector archways failed to spot his weapon.

Amsterdam's Schiphol Airport has at least 15 full-body millimeter wave scanners that see underneath passengers' clothes to detect suspicious packages or weapons.

The problem: their use has been only voluntary because of concerns that the scans reveal passengers naked to the operators and anyone else passing by the machine's screen.

The costs are also substantial. Whereas a traditional archway metal detector runs up to $15,000, more intensive whole-body scanners cost about 10 times as much.

I don't anticipate myself that there'll be a rush to buy new equipment because airport operators are strapped for cash at the moment and the equipment itself, whilst good, is not a solution to the problem, said Kevin Murphy, product manager of physical security for Qinetiq Group, a British-based defense and security technology group.

Some passengers are reassured that there's new technology there and are prepared to give up some measure of their privacy for it, and others have been outraged by it.

Airport operators need effective security plans, behavioral modeling and hiring processes just as much as they need advanced hardware, he told Reuters. Qinetiq is focusing its efforts on standoff screening that scans passengers even before they reach security checkpoints.

SEEING UNDER CLOTHES

Both millimeter wave and backscatter X-ray scanners try to do roughly the same thing -- see under clothes and identify unusual objects by their different densities relative to the human body.

Industry experts say public fears about radiation from the X-ray machines are unwarranted. But stronger than the health concerns are the privacy fears, in the United States and especially in Europe.

Germany's interior ministry, which sets the standards for domestic airport security, declined to use body scanners last year after it decided they were an invasion of privacy, although their usefulness and safety are still being tested.

They were rejected as going too far into the private sphere of travelers, said Verena Meyer, spokeswoman for the Federal Commissioner for Data Protection and Freedom of Information, an independent parliamentary watchdog.

An interior ministry spokeswoman said on Tuesday that certain conditions had to be fulfilled, including masking people's intimate details and making explosives more easily recognizable.

In Britain, Home Secretary Alan Johnson said: We intend to be at the cutting edge of all this new technology and to ensure that we put it in place as quickly as possible.

But progress until now has been slow. A spokesman for Manchester airport said it was running trials but had made no decision on implementation, while Heathrow operator BAA said it was not using body scanners at all.

The European Parliament has consistently opposed body scanners on privacy and health grounds and has asked for more studies in both these areas.

Nonetheless, there are no EU rules preventing member states from using them if they want to, a spokesman for the Commission said on Tuesday.

NO GUARANTEES

Speculation about increased demand has boosted shares of scanner makers this week. Some smaller companies such as ICX Technologies and OSI Systems, worth only a few hundred million dollars to begin with, rose 10 percent or more on Monday.

Larger players like Smiths Group and L-3 Communications have also benefited, with their machinery already in trials in airports around the world.

Schiphol's chief operating officer and director of security said on Monday they intend to make millimeter wave scanners mandatory once they get EU approval. Schiphol officials rejected X-ray machines as too unsafe for the public for regular use.

They stressed repeatedly that no matter what technology they chose, they could not be certain last week's outcome would have been any different.

There is no 100 percent guarantee we would have caught him, Schiphol Group COO Ad Rutten said of Abdulmutallab.

The industry was quick to praise Schiphol's decision but just as quick to add that it might not be enough.

Absolutely without a shadow of doubt this is a good thing. But one solution will not address every vulnerability. It needs to be a set of solutions, said Jane's Aviation analyst Chris Yates.

($1=.6256 Pound)

(Additional reporting by Madeline Chambers and Brian Rohan in Berlin, Luke Baker in Brussels, Adrian Croft, Bill Maclean and Eric Auchard in London and Gilbert Kreijger in Amsterdam; editing by Mark Trevelyan)

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