People still need more than their faces to enter and exit America on international flights, but a growing number of early-stage facial recognition deployments that aim to screen passengers with little human intervention are rolling out at airports across the country.

At Hartsfield-Jackson Airport in Atlanta, a multifaceted facial recognition system and process that scans passengers’ biometrics to verify their identities at various points throughout the airport offers an ultramodern glimpse into document-free but face-scan-enabled travel—as well as the privacy implications that could accompany it.

“The neat thing about what they're doing in Atlanta is that different players within the airport environment are plugging into the same [Customs and Border Protection]-created backbone—this Traveler Verification Service—to accomplish different identity verification functions throughout the airport,” Adam Klein, the Trump-appointed chairman of the Privacy and Civil Liberties Oversight Board, told Nextgov Thursday.

Late last year the independent executive branch agency shared its observations of a biometric pilot at McCarran International Airport, which were captured as part of the ongoing examination of how biometrics are used to validate passenger identities at each phase of travel. Last week, Klein detailed members’ recent visit to Atlanta’s airport, where they assessed CBP’s biometric exit program and Delta’s fully biometric terminal—the first of any American airline.

“The Traveler Verification Service is the backbone of all those applications that we saw at the Atlanta airport,” Klein said.

Following a 9/11 Commission-led investigation, in 2004 Congress required CBP to build a biometric system to validate that visitors to the U.S. depart in accordance with the terms of their entry. To do so, the agency produced the Traveler Verification Service, or TVS. Klein said the system is already used beyond Atlanta, at some gates at the Dallas/Fort Worth International, Los Angeles International, Dulles International, and John F. Kennedy International Airports, with more to be added to the list this year. Essentially, TVS uses existing photos of foreign visitors to the country and of travelers booked on international flights—such as their passport or visa photos—to enable CBP officials to conduct facial recognition checks as people leave, Klein said. Though the agency owns the backend of TVS, the Homeland Security Department is responsible for storing biometric information, the State Department maintains the passport photos and visa photos, and a commercial contractor provides the technical implementations.

While the TSA pilot that the privacy board observed at McCarran was merely a test that did not store passenger photos, the CBP, TSA and Delta terminal biometric programs members saw this time around are “fully plugged in and operational.” Various facial recognition activities in Atlanta’s aviation security process tap into this one streamlined service. TVS—as Klein described it—assembles galleries of passport and visa photos belonging to people who are known to be departing on international flights that day, as well as photos from previous entries.

“Those photos provide enough of a basis for the system to compare your live face and verify that it's actually you,” Klein said.

It’s currently limited to travelers embarking on international flights, but Klein detailed all that the airport’s nascent process for biometric exit verification via facial recognition encompasses: Upon arrival, Delta’s fully biometric terminal allows passengers to use their face at a biometric-reading kiosk to check in. That kiosk connects to TVS for validation. Travelers then move to TSA security checkpoints where instead of presenting identity documents, passengers present their faces and a TSA-owned tablet will connect to TVS to confirm their identity. Finally, passengers move to their boarding gates, where Delta-owned tablets that are also connected to the system are used for one last confirmation before they depart on the flight.

“The advantage of Atlanta is that it combines really every significant application of the CBP system for international travelers. You've got this airline partnership with Delta, which is very, very developed. You've also got the partnership with TSA, where TSA is borrowing that system to use for international travelers,” Klein said. “We watched a large international flight board and I would say in general, as you would expect, people's primary concern was just getting on the plane.”

One crucial component of the privacy board’s comprehensive study is evaluating how people respond to TVS and the budding technology. Klein said in this flight’s case, passengers were told that they could opt-out of using facial recognition and a few people did decide to board “the old fashioned” way. Still, the team observed that most who were boarding that international flight opted to use only their faces and the tech. For virtually all of those travelers, Klein said the system positively matched the travelers in a couple of seconds—which he viewed as “strikingly fast.”

“Many people seemed surprised that they did not then have to present any other documents,” he said.

The board will also assess implications around bias and fairness that accompany the various facial recognition technology deployments. On top of how the algorithms and system itself perform across different ethnicities and social groups, Klein said it’s also critical to determine whether the programs are perceived as fair by the public—“because if people perceive it to be dropping errors disproportionately into the lap of one social group, then that would obviously undermine public faith in the system significantly.” In that light, Klein said members are honing in on potential bias by reviewing CBP’s internal studies on the issues, technically evaluating the algorithms being used, and addressing a separate but related question about whether the physical environment in the airport (because of the lighting or cameras’ positioning) could skew results across various races.

“The agency says that they have not seen any discriminatory effects in their analyses,” Klein said. “And we're reviewing those analyses and making sure that all the relevant factors are being considered here.”

The privacy board is also working to ensure that TVS might not be misused to perform other functions and they’re looking into potential security vulnerabilities. For now, he said, Americans’ photos only stay in the system for 12 hours at a time, and that time period could soon be reduced. He added that the photos taken throughout the process are not stored on the local devices.

“My initial impression is that the agency is taking [security] quite seriously as well,” he said.

Before completing the project, the board will assess biometric efforts at airports in the DC-metro area, and engage experts from non-governmental organizations, privacy and civil liberties groups, as well as technical experts and academic researchers. They’ll also host at least one public event in the coming months to bring people together to further discuss the board’s impending analysis.

As for the publication of the entire comprehensive review, it’s coming soon. “We hope that we will have something—whether its initial findings or some other product—by the end of the summer,” Klein said.