The Transportation Security Administration is rolling out the next-generation security scanner that it says uses a new, less controversial technology to take full body scans of airline passengers.
The new scanner will begin testing today at Arizona's Phoenix Sky Harbor Airport.
Passengers who are singled out for further screening will be offered the scanner, instead of the full-body pat down they are usually subjected to.
The TSA installed the new "millimeter wave" scanners in Phoenix, just nine months after the same airport was used to introduce its first pilot program, which used the disputed "backscatter" X-ray technology.
Privacy advocates decried these earlier machines, which use radiation to scan passengers as excessively invasive.
The new scanners use what's called a millimeter wave technology that employs electromagnetic waves versus the backscatter's radiation wave.
The TSA describes the images from the new machines as a like a "fuzzy photo negative."
But Barry Steinhardt, director of the American Civil Liberties Union, who has seen the new machines, told The Associated Press, the images are "… more graphic than that. I continue to believe that these are virtual strip-searches."
The government awarded L-3 Communications a contract in July to develop a passenger screening machine using the new electromagnetic wave technology. Millimeter uses radio waves that reflect off a human body and bounce back in just a matter of 1.8 seconds, creating a 3-D holographic image.
The TSA has purchased eight of the machines for $1.7 million. The agency says that testing the millimeter wave machine against the earlier backscatter technology will help it compare the reliability and functionality of both technologies.
Released in February, the backscatter machines currently in use are manufactured by American Science and Engineering.
Backscatter allows TSA agents to view an almost instantaneous X-ray-like view of a passenger's body. It is those high-resolution images that have drawn concern from privacy and civil liberties groups.
In a statement to Congress last year, the ACLU's legislative counsel, Timothy D. Sparapani, noted the technology's potential for screening baggage and cargo, but urged Congress to prohibit the use of the technology as part of routine screening due to privacy concerns.
Sparapani said the images generated require passengers "to display highly personal details of their bodies," which he said shouldn't be necessary "as a prerequisite to boarding a plane."
TSA says it has worked with manufacturers to modify the images captured and maintains that the machines used in the screening method, which is a voluntary alternative to a physical pat down, does not allow the machine operator to print, store or send out the image taken.
According to the TSA, most passengers it surveyed said they preferred to have a body screening rather than a pat down.
"What we have seen in Phoenix since February is about 79 percent of the people are electing to try the passenger imaging technology," TSA spokeswoman Ellen Howe told ABC News.
The millimeter wave machine, Howe says, takes into account the passengers' right to privacy by taking several measures to help passengers feel more secure.