US Customs and Border Protection (CBP) is set to expand the use of facial recognition tech to identify just about every person leaving the United States on a commercial flight.

As Quartz reports, the CBP already uses facial recognition technology at 15 US airports. The system works by capturing a photo of a passenger as they approach their airport departure gate. The image is then compared to visa and passport applications for a possible match so as to create an "exit record." No match flags the individual for closer inspection by the CBP.

In the Fiscal Tear 2018 Entry/Exit Overtstay Report released by Homeland Security, it's stated (on page 11) that CBP intends to expand the use of this so-called biometric exit over the next four years to, "97 percent of departing commercial air travelers from the United States." The reason? The technology is highly reliable and therefore very good at detecting individuals who are classed as overstays on a visa.

The 15 airports already using facial recognition have had 15,000 flights and over two million passengers pass through the biometric exit system. Of those, over 7,000 passengers were detected as overstays. Considering the system only started being used in 2017, you can see why CBP views facial recognition as an important tool for use across all airports. The system was also key to identifying an imposter last year and blocking his entry into the US.

For now, any airport not using the new tech will continue to rely on departing airline flight manifests. However, once installed across all US airports it's thought the same technology will start being introduced at land borders, too.