The same type of equipment that is now the focus of tighter airport security measures after the Christmas Day plane bombing attempt over Detroit was given a test run at Kennedy Airport in the summer of 2008, federal authorities said.

Officials with the Transportation Security Administration began using millimeter wave body scanners at randomly selected airports, including Kennedy, to test their efficacy, said Ann Davis, a TSA spokeswoman.

Passengers chosen by TSA workers in security check-in lines were given the choice of being scanned or patted down.

After the field testing was complete, the TSA removed the body scanner that was at the Delta Air Lines terminal, which is not unusual, Davis said.

"We need to test them in various operational environments - different temperatures, different passenger volume," Davis said.

Davis said she couldn't provide the date the scanners were removed from Kennedy Airport. Delta Airlines officials declined to comment on the use of the scanners.

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Wednesday, the Netherlands announced it would immediately begin using full-body scanners for flights bound for the United States.

Dutch officials said that the equipment could have stopped would-be bomber Umar Farouk Abdulmutallab, who authorities said boarded Northwest Airlines Flight 253 to Detroit from Amsterdam's Schiphol Airport on Friday carrying undetected explosives.

The 23-year-old Nigerian allegedly tried but failed to blow up the airliner, which carried 239 passengers.

The TSA has said it has purchased 150 full-body scanners using backscatter technology and plans to install them at airports nationwide in 2010.

There are longer-range plans to purchase 300 more. The TSA hasn't released when or in what airports the new machines will be installed.

Body scanners that peer underneath clothing have been available for years, but privacy advocates say they are a "virtual strip search" because they display an image of the body onto a computer screen. The machines can scan for explosives and weapons hidden underneath clothing.

Privacy advocates have balked at use of the machines in the United States, saying that more needs to be done to protect the images.

Images are transmitted to monitoring screens separated from where the passenger is scanned, Davis said, faces are blurred and images cannot be stored."We have the security office in a remote location," Davis said, adding the machines have no image "storage capability."

Alvy Dobson is the former director of aviation security at Love Field in Dallas and a former TSA officials who now works in private industry. More use of full-body scanner will be a big part of aviation security in the future, he said.

"I think that is certainly the way to go in an attempt to stay ahead of the people who want to do us harm," Dobson said.