Five-hundred body scanners, split about evenly between the two technologies, are deployed in U.S. airports. The X-ray scanner, or backscatter, which looks like two large blue boxes, is used at major airports, including Los Angeles International Airport, John F. Kennedy in New York and Chicago's O’Hare. The millimeter-wave scanner, which looks like a round glass booth, is used in San Francisco, Atlanta and Dallas.
Within three years, the TSA plans to deploy 1,800 backscatter and millimeter-wave scanners, covering nearly every domestic airport security lane. The TSA has not yet released details on the exact breakdown.