A shimmy toward the body scanner, a step into the booth and a wave of the arms _ routine procedure now at U.S. airports, but not necessarily in Europe.

In the wake of a foiled al-Qaida plot to bomb a jet heading to the U.S., it's unclear whether cash-strapped Europe has the latest security equipment to thwart an airliner attack, or whether machines will be able to keep up with determined terrorists.

With the summer Olympics expected to draw millions of visitors to London, airport security has taken on renewed urgency. A look at the issues:

THE DEBATE

Terror groups bent on blowing up U.S.-bound jetliners are experimenting with explosives that use non-metal detonators. That means bombs might be missed by traditional metal detectors used at most international airports. The question is whether to switch to newer, expensive and more intrusive scanners.

There are two types of full-body scanners in wide use in U.S. airports. Backscatter X-ray scanners employ advanced imaging technology and small doses of ionized radiation to detect objects concealed underneath a person's clothing. Millimeter wave scanners use radio frequencies for the same purpose.

Peter Kant, executive vice president of Rapiscan Systems, which makes the Backscatter, says the machines have fewer blind spots, are fast and can detect both metal and other potential explosives concealed on someone's body, though it's unclear whether they can spot explosives inside someone's body cavity. The downside is they are expensive and some critics have questioned their safety.

Experts say trials of the millimeter wave technology in Rome and Helsinki have resulted in frequent false alarms and delays.

In airports outside the U.S., most passengers simply go through metal detectors and have their carry-on luggage scanned.

"There is a concern that overseas security doesn't match ours. That's an ongoing challenge," says House Intelligence Committee Chairman Mike Rogers, a Republican from Michigan.

EUROPEAN RESISTANCE

Europe has never required full-body scans, and efforts to install U.S.-style backscatter machines were stalled last year when the European Commission ordered a study into their safety.

An independent body has since found that little risk is involved.

But it's too soon to say when _ if ever _ advanced machines might be installed in European airports. Some cost more than $160,000, and in cash-strapped Europe, that's a hefty price.

Even in Britain, which can opt out of some EU dictates, there are only 20 or so backscatter machines. And those are only in trial usage.

In the United States, the Transportation Security Administration "is both the customer and the operator, whereas in Europe and other regions the regulator sets requirements and the airport picks up the bill," says Ben Vogel of IHS Jane's Airport Review. "The mix of stakeholders in Europe often leads to divergent positions on embracing technological change."

France's Charles de Gaulle Airport experimented with full body scanners in 2010 but decided against them.

"We determined that the automated detection software was not reliable enough," says Eric Heraud, a spokesman for the French civil aviation authority DGAC and the Paris airport authority.

So are the current systems enough to stop a terrorist?

"No system is 100 percent reliable. You have to constantly adapt and improve any system," Heraud says.

Millimeter-based scanners have undergone trials at Amsterdam Airport Schiphol, where the so-called underwear bomber passed undetected on Christmas Day in 2009. The plot was thwarted when Nigerian Umar Farouk Abdulmutallab failed to ignite the explosives aboard a Detroit-bound jet.

There are more than 400 commercial airports in Europe, but only a small proportion handle trans-Atlantic traffic.

TERRORIST TECHNOLOGY

First, it was smuggling explosives in drink bottles in a trans-Atlantic plot to blow up several U.S.-bound planes in 2006. Then it was the Nigerian underwear bomber in 2009.

A year later terrorists tried to blow up explosive-packed printers bound for Chicago-area synagogues using the alarm function of two cell phones wired to syringes full of lead azide, a moisture-resistant powder that takes only a small electric charge to explode _ much like the bomb in the latest plot.

"You can basically hit or heat it," says Neil Gibson, an explosives expert. "It's unlike other substances that break down or are more volatile."

European security officials say al-Qaida in the Arabian Peninsula is determined to target U.S.-bound airliners _ but not necessarily flights inside Europe.

"At this point, the likelihood of an overseas attack in Europe from al-Qaida seems less likely than other scenarios," says a European security official, who spoke on condition of anonymity because of the sensitivity of his job. "But they definitely have the intent for all sorts of attacks and it appears their capability is increasing."

OLYMPIC WORRIES

The Olympic torch arrives in Britain next week with a controversy already raging over U.K. border security.

Staff shortages, poor planning and a fear of racial profiling are being blamed for chaos at some of the country's busiest airports, according to John Vine, the independent chief inspector of borders and immigration who issued a damning report on the problems Thursday.

Britain's government has previously acknowledged that security equipment at airports is only about 60 percent effective in detecting potentially hazardous items.

Still, the investment in Olympics security has been massive. Troops, armed police, warships and air-to-surface missiles will all be on standby to protect the public.

Security officials are planning for an array of potential nightmares during the games _ a water-based offensive from the Thames, an airline attack using a hidden bomb or a homegrown attack like the 2005 suicide bombings that killed 52 people during London's busy rush hour.

One of their biggest fears, however, is a lone-wolf terrorist who stays off the radar until he strikes.

Other possibilities exist, too, such as a remote-controlled aircraft carrying deadly poison, according to British military Lt. Col. Brian Fahy, responsible for community relations during the London Games.

While Rapiscan, based in Torrance, Calif., is a key security partner for the Olympics, its full-body advanced scanners won't be used at the games.

"We are providing all of the X-ray and security equipment, but body scanning is not part of this," says Kant, the Rapiscan executive. "We know _ we believe _ the amount of security and the level of security being provided is very high. I think more than just the Olympics, what the Yemen plot has shown us is that the plot is very real _ there are known gaps _ and it needs to be taken into account."

ASK THE EXPERTS

It may not be polite or politically correct but it works, say the Israelis.

The grilling of passengers boarding planes bound for Israel begins at the airport with a litany of security questions. After that, it's not unusual to have a body search in a private room and an equipment search. It goes without saying most passengers are scanned before they get on the plane.

But the process doesn't necessarily stop at departures.

Sometimes upon landing, passengers are herded into rooms where their liquids are squirted out, computers disassembled and batteries removed. And Israeli security agents make no apologies for profiling.

"The system knows about a suspect long before they arrive at the airport, which is something that doesn't happen at many airports around the world," says a senior Israeli airport security official, speaking on condition of anonymity because of security protocol.

"The cons in this are that it breaches people's privacy to a certain extent and also the system costs a lot of money to run."

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Associated Press writers Angela Charlton in Paris, Ian Deitch in Jerusalem, David Stringer in London and Slobodan Lekic in Brussels contributed to this report.