The U.S. Transportation Security Administration began a test of body scanning machines at Oklahoma's Tulsa International Airport Wednesday.
Instead of walking through metal detectors, airline passengers in Tulsa will be screened by a machine that can look through clothing to detect hidden weapons, USA Today reports.
The experimental program will help the TSA decide whether the $170,000 devices should replace metal detectors that have been in use since 1973.
The scanners are able to detect non-metallic weapons like plastic and liquid explosives that the TSA considers a major threat.
They work by bouncing harmless "millimeter waves" off passengers' bodies but raise privacy concerns because their images reveal outlines of private body parts.
"We're getting closer and closer to a required strip-search to board an airplane, says Barry Steinhardt of the American Civil Liberties Union.
During the next two months, the TSA plans to test the devices at airports in San Francisco, Las Vegas, Miami, Albuquerque and Salt Lake City.