Seconds after a passenger stepped through an advanced-imaging machine at a BWI Marshall Airport security checkpoint, an image of a human body popped up on a video screen.

It did not show the passenger's body as it appears under his clothing. No physical imperfections or private parts were in sight. And that is the point of the new technology demonstrated Friday at Baltimore-Washington International Thurgood Marshall Airport.

The image, displayed where both the passenger and a security officer could see it, bore little resemblance to the graphic depictions of individuals that have aroused the anger of many fliers. The screen simply showed a cartoonlike depiction of the human form, with a little yellow box superimposed over one of the passenger's legs — an area that needed to be checked further.

BWI is one of about a dozen U.S. airports where the Transportation Security Administration has deployed the new security software, and the agency hopes it will put to rest widespread complaints about a screening regimen that critics have labeled a "virtual strip search."

Among other things, the new software will eliminate the need for a TSA officer to be stationed in a screening room off the checkpoint — much like the Wizard of Oz behind his curtain — scrutinizing images of each person who passes through the machines.

The software was put into operation this week in 10 advanced-imaging machines already installed at BWI, and the rollout is part of an effort by the TSA to eliminate the creepiness factor from the enhanced screening program it adopted to detect explosives. The federal agency is spending $2.7 million to install the new program in 240 machines at 40 airports by this fall.

The "passenger" during Friday's airport demonstration was a TSA employee, and the yellow box told the security officer that the machine had detected something to be checked.

In this case, it turned out to be a penny in the man's pocket.

TSA spokesman Kawika Riley said the new software is just as effective as the version that provided a more graphic image of how people look under their clothes. "It meets the same security standards as it did before," Riley said.

TSA and airport officials invited the news media to the demonstration at the international terminal, letting reporters see how the software reacts when something suspicious is detected on a passenger.

TSA employees went through the imaging machine and held up their hands just as passengers have been doing since the devices were installed at the airport a few years ago.

After being scanned, they stepped through the device and were asked to wait a few seconds while images were processed. If nothing was found, all that showed up on the screen mounted on the outside of the device were the letters "OK" on a green field.

If the device detects what the TSA calls an "anomaly," the image that comes up is worthy of a "G" rating. Unlike the old system, in which the screener in the adjoining room could determine whether the scanned person was fat or thin, tall or short, and endowed with male or female organs, the new software erases all individuality.

"We've gotten rid of that viewing altogether. The software essentially does all the work for us," Riley said.

As the "passengers" moved through the checkpoint, TSA officers who took part in the demonstration confined their pat-downs to areas of the body where concerns were raised. When a woman came through and a yellow box showed up on the image on the screen, the officer performed a pat-down of the area and determined that the anomaly was merely a bra clasp.

"Thank you, sweetheart. Have a nice day," the female officer said.

Riley said the TSA believes the software change will allow passengers to move through security more quickly. One reason, he said, is that the officer at the checkpoint can see precisely where a problem has been detected. With the old software, he said, the officer had to receive verbal instructions from the viewing machine operator about which areas of the passenger's body to check.

In the long run, Riley said, the change probably will save the government money.

"With this technology there's no longer any need to have an officer assigned to a remote viewing room," Riley said. He added that the TSA would save on the costs of building and maintaining such rooms.

BWI Executive Director Paul Wiedefeld said the airport could put any square footage freed up by the elimination of the remote viewing rooms to good use.

Wiedefeld said the change to the advanced-imaging program is a welcome development. "Last Thanksgiving, there was almost a passenger revolt over this technology," he said.

The new procedures provide "a better experience for the customer," the airport chief said. "They see the same imaging the screener sees, so that takes some of the mystery out of this technology."

The new technology has been deployed at four of BWI's five piers — A, B, D and E. The checkpoint on Pier C, at the oldest part of the airport, has not been equipped with the advanced-imaging machines because the devices won't fit until an expansion project is completed in several years.

The software upgrade is being introduced only at airports that use the "millimeter wave" version of advanced-imaging software. Passengers who pass through airports equipped with the other version of the technology, known as "backscatter," will still encounter the more intrusive scan — though they can choose a pat-down instead.

Speaking for one of the chief critics of the TSA's screening program, American Civil Liberties Union legislative counsel Chris Calabrese said the new technology is an "important step forward."

"At least the employee is not looking at the naked person every time," he said. "We appreciate their listening. Obviously, we wish they had done it sooner."

Calabrese noted that the software upgrade does not apply to backscatter machines at airports around the country. "We're only halfway there," he said.

The ACLU spokesman said the software fix doesn't alleviate all of the group's concerns about the airport security program. "We still have very intrusive pat-down practices and groping procedures," he said.

Passengers who object to the advanced imaging are permitted to choose pat-downs instead, but the TSA has warned that those searches can be uncomfortably thorough.

The Electronic Privacy Information Center says the main issue is what is done with the information gathered by the screening device.

Lily Coney, EPIC's associate director, said the software change is a "step in the right direction" but concerns remain.

"They haven't taken out the image capture capability," she said. "They're just showing you a different presentation of the same data."

EPIC, which has taken the TSA to court over the issue, still wants a formal process to write rules governing how the technology will be used, Coney said.

Riley said some of EPIC's concerns about the technology are misplaced.

"It cannot store, it can't transmit images, period," he said.

The TSA spokesman defended the agency's use of the old technology to this point, saying it had to move forward with the "best available technology" to deal with potential threats to aviation,

Riley said the TSA intends to replace the imaging software in the backscatter machines.

"We're moving toward it right now," he said, declining to offer a timetable.

michael.dresser@baltsun.com