Federal officials say they are expanding tests to speed up airport lines and improve security.
The Transportation Security Administration said Tuesday that it plans to begin using computed-tomography or CT scanners to inspect carry-on bags at the Phoenix airport by the end of the year.
CT scanners are already used to screen checked baggage.
TSA says it will work with American Airlines to make other changes to speed up screening this fall in Chicago, Dallas, Los Angeles and Miami.
The agency says the scanners and other steps will cut the time travelers spend in line by about 30 percent.