Six major airports in the United States are participating in pilot programs that require Americans traveling abroad to submit to facial-recognition scans when leaving the country, the Associated Press reported.

Airports in Boston, Chicago, Houston, Atlanta, New York City and Washington, D.C. have all started to implement the biometric scanning procedures, with plans to expand the program to a number of other high-volume international airports across the country by the start of next year.

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News of the biometric scans being active at airports and used to scan American citizens prior to boarding their flights is the latest development in the increased effort by the Donald Trump administration to implement strong vetting procedures for those coming and going from the country.

U.S. Customs and Border Protection’s (CBP) Larry Panetta spoke about adoption of facial recognition technology earlier this year at the Border Security Expo, where he suggested there was already enough information in the government’s systems that facial recognition technology could already identify many travelers.

“We currently have everyone’s photo, so we don’t need to do any sort of enrollment,” Panetta said at the event. “We have access to the Department of State records so we have photos of US Citizens, we have visa photos, we have photos of people when they cross into the US and their biometrics are captured into [Department of Homeland Security database] IDENT.”

The plan discussed by Panetta is known as Biometric Exit, which would require passengers to have their photos taken before boarding a plane. That photo would be cross-referenced with a database of photos to confirm the traveler’s identity.

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Biometric Exit was first confirmed to be used in Atlanta on flights heading to Tokyo and the Trump administration had planned to expand its use over the course of the summer. The expansion was first laid out in the President’s executive order that also banned travelers from seven majority-Muslim countries.

The confirmation of additional airports using biometric scans comes from the Department of Homeland Security (DHS), which said U.S. citizens would also be subject to the facial recognition scans—an expansion of a 2004 biometric tracking law designed to target foreigners entering the U.S.

John Wagner and Michael Dougherty, officials at CBP, told a House subcommittee in May that U.S. citizens are not exempt from the biometric scans because “is not feasible to require airlines to have two separate boarding processes for US citizens and non-US citizens” and “to ensure US citizen travelers are the true bearer of the passport they are presenting for travel.”

While the officials promised photographs of U.S. citizens that match the photo of a U.S. passport holder are discarded “after a short period of time,” Wagner also said those photos may be stored after going through “the appropriate privacy reviews and approvals."

In a privacy assessment published by DHS in June, the agency noted the "only way for an individual to ensure he or she is not subject to collection of biometric information when traveling internationally is to refrain from traveling." A 2016 study conducted by Georgetown found half of adult Americans are already in biometric databases.