Next Time you fly... you may as well fly... naked!

BALTIMORE — Body-scanning machines that show images of people underneath their clothing are being installed in 10 of the nation's busiest airports in one of the biggest public uses of security devices that reveal intimate body parts.

The Transportation Security Administration (TSA) recently started using body scans on randomly chosen passengers in Los Angeles, Baltimore, Denver, Albuquerque and at New York's Kennedy airport.

Airports in Dallas, Detroit, Las Vegas and Miami will be added this month. Reagan National Airport in Washington starts using a body scanner today. A total of 38 machines will be in use within weeks.

"It's the wave of the future," said James Schear, the TSA security director at Baltimore/Washington International Thurgood Marshall Airport, where two body scanners are in use at one checkpoint.

Schear said the scanners could eventually replace metal detectors at the nation's 2,000 airport checkpoints and the pat-downs done on passengers who need extra screening. "We're just scratching the surface of what we can do with whole-body imaging," Schear said.

The TSA effort could encourage scanners' use in rail stations, arenas and office buildings, the American Civil Liberties Union said. "This may well set a precedent that others will follow," said Barry Steinhardt, head of the ACLU technology project.

Scanners are used in a few courthouses, jails and U.S. embassies, as well as overseas border crossings, military checkpoints and some foreign airports such as Amsterdam's Schiphol.

The scanners bounce harmless "millimeter waves" off passengers who are selected to stand inside a portal with arms raised after clearing the metal detector. A TSA screener in a nearby room views the black-and-white image and looks for objects on a screen that are shaded differently from the body. Finding a suspicious object, a screener radios a colleague at the checkpoint to search the passenger.

The TSA says it protects privacy by blurring passengers' faces and deleting images right after viewing. Yet the images are detailed, clearly showing a person's gender. "You can actually see the sweat on someone's back," Schear said.

The scanners aim to strengthen airport security by spotting plastic and ceramic weapons and explosives that evade metal detectors and are the biggest threat to aviation. Government audits have found that screeners miss a large number of weapons, bombs and bomb parts such as wires and timers that agents sneak through checkpoints.