Most U.S. airports will have facial recognition technology in the next four years.

The United States Department of Homeland Security says the U.S. Customs and Border Protection will install biometric exit technology in almost all commercial airports. The CBP hopes to use biometric exit technology on more than 97 percent of commercial air travelers departing from the United States to help it find people who overstayed their visa.

As of September 2018, only 15 U.S. airports were equipped with this facial-recognition technology. Those airports used the technology on more than 2 million passengers, finding 7,000 who overstayed their visa.

CBP checks visas via biographic manifest data or the name and passport number. But the biometric system would likely be more efficient, as CBP claims it has a 98 percent match rate.

Others argue the technology isn’t actually that successful. Facial recognition doesn’t work as well for people of color, which the ACLU tested in 2018. Further, a report by the CAPA-Centre for Aviation found facial recognition software “is not so good at identifying ethnic minorities when most of the subjects used in training the technology were from the majority group.”

People wearing glasses, hats, scarves or sporting facial hair or weight changes also affect the accuracy.