The Transportation Security Administration (TSA) will expand its facial recognition program to around 430 US airports over the next several years following what it calls “extremely promising” results in its pilot program, according to Fast Company. The agency reportedly said its program yielded 97% effective results across all demographics, including those with dark skin. The program is currently in use in 25 airports.

As pointed out in Fast Company’s story, a 97% effectiveness rate across more than two million airline passengers per day means that, for over 60,000 of those people, the biometrics won’t work properly if it’s used in every airport in the country.

At the moment, the pilot program is officially voluntary. It uses 1:1 matching — that is, it compares your face in the moment against your government-issued ID like a driver’s license or a passport. The TSA says that data is immediately overwritten when the next passenger moves up, and that at the end of the day, no images are saved.

The TSA is also running a separate pilot at two of its airports that instead compares a traveler’s image against a government database. Only “trusted travelers” such as those enrolled in TSA PreCheck are included in this pilot.

The Electronic Privacy Information Center (EPIC) says there are reasons to be concerned about facial recognition software being used by government agencies that go beyond its efficacy among different demographic groups. EPIC says the US has no overarching laws when it comes to its use of facial recognition tech, putting travelers’ civil rights and privacy at risk.

Eventually, the TSA would like biometric recognition to be mandatory. During a South by Southwest (SXSW) fireside chat earlier this year, TSA Administrator David Pekoske said it would eventually be required across the board, citing effectiveness and efficiency. He also said “in our own testing, we show no statistically-significant variation across demographic groups,” going on to say the TSA wants to be as transparent as it can about the program. However, the agency told Fast Company it will not release the results of its two years pilot testing publicly.

During the SXSW talk, when Dallas Morning News reporter Kyle Arnold asked if anyone directed the TSA to initiate this program, Pekoske said it was a self-directed initiative.