The Transportation Security Administration and American Airlines are testing a 3-D carry-on bag screener in Phoenix, technology they hope will eventually allow travelers to keep liquids and laptops in their bags and speed up the screening process.

Sky Harbor International Airport is one of two U.S. airports to add a computer tomography (CT) scanner at a security checkpoint. Boston’s Logan Airport is the other.

The technology, which gives TSA officers a clearer picture of a bag’s contents, is widely used to screen checked bags, but until recently, the machines have been too large for security checkpoints.

American, which has a hub at Sky Harbor, said the new CT screening equipment shoots hundreds of images with an X-ray camera that spins around the conveyor belt, providing three-dimensional views. The airline said the system uses algorithms to better detect explosives, firearms and other banned items.

The X-ray scanners currently in use at the checkpoints offer two-dimensional views.

The pilot program was announced a year ago with initial plans to install the machines by the end of 2016.

In Phoenix, the CT scanner is in one of the screening lanes at the B checkpoint in Terminal 4. The B gates are home to some of American’s flights.

During the testing period, travelers going through the B gates will be asked if they are willing to participate, TSA spokesman Nico Melendez said. One passenger at a time will have his or her carry-on bags go through the system. Passengers still will be required to take laptops and liquids out of their bags.

“We are proud to be working collaboratively with the TSA to add new technology to the screening process,”  Kerry Philipovitch, American’s senior vice president of customer…