Delta Air Lines is rolling out facial recognition for some domestic travelers at its Detroit hub, an expansion of the biometric technology beyond international flights.

The move comes after Atlanta-based Delta launched in 2018 what it called a “biometric terminal” for international travel using facial recognition at Hartsfield-Jackson’s Maynard H. Jackson International Terminal. The system uses U.S. Customs and Border Protection’s traveler verification service, which has a database of travelers’ photos from their passports.

For domestic travel, passengers often use driver’s licenses from different states as their ID to fly, so there isn’t a complete national database of photos to draw on for facial recognition.

In Detroit, Delta is launching facial recognition as an option for domestic travelers who have passport numbers, are members of the Transportation Security Administration’s PreCheck trusted traveler program, and who store that information in their Delta app SkyMiles profile.

Starting this month, customers in Detroit who meet those requirements can opt in via the Delta app and go through a dedicated TSA PreCheck checkpoint using facial recognition in place of a physical ID and boarding pass.

Delta said the program is voluntary, and those who don’t want to use facial recognition can choose to not opt in at check-in.

The airline plans to expand facial recognition to bag drop and boarding in Detroit this spring for a “more touchless airport experience.” It plans to eventually expand facial recognition to the rest of its network, according to Delta chief customer experience officer Bill Lentsch.

Spirit Airlines is testing facial recognition at Chicago O’Hare and New York’s LaGuardia Airport, but still requires passengers to show ID as they approach the self bag-drop as TSA validates the system’s effectiveness.

Miramar, Fla.-based Spirit said Atlanta is on its list of airports to deploy the technology when it rolls out further. Hartsfield-Jackson has started preparations for tests of facial recognition for domestic travel.

Other travelers who are members of the Clear trusted traveler program have for years used biometrics including fingerprints, facial recognition or iris scans as a substitute for ID, though they still must scan a boarding pass. ID is required to check bags for domestic flights and a boarding pass is required to board domestic flights.

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