Face scans have officially replaced paper boarding passes and passports for travelers flying to select international destinations out of Atlanta’s Hartsfield-Jackson International Airport.

Delta Air Lines has unveiled the first all-biometric terminal. Travelers on certain international flights will use their faces to check baggage and board their flight. Delta, Aeromexico, Air France, KLM and Virgin Atlantic Airways are the airlines using the technology for flights that operate out of Hartsfield’s Terminal F.

“Delta’s successful launch of the first biometric terminal in the U.S. at the world’s busiest airport means we are designing the airport biometric experience blueprint for the industry,” Delta CEO Gil West said last week.

The airline, which already had some of the technology in place leading up to the launch this month, said about 25,000 passengers move through the terminal each week and most are already taking advantage of the technology. Only about 2 percent of travelers opt out. Delta will expand the biometric program to its hub in Detroit next year.

Here’s how the system in Atlanta works: Passengers traveling through Terminal 7 enter their passport information when they check in online. Then, when they approach a kiosk in the lobby, a camera at the counter in the lobby or the Transportation Security Administration security checkpoint, they click “Look” when it appears on the screen. The device takes their picture – and if a green check mark flashes on the screen, they proceed through the system. Travelers’ pictures are compared with a Customs and Border Protection database.

An increasing number of airports are using biometrics to process passengers as they move through the system. Dulles International Airport recently unveiled a system that uses iPads to scan passengers’ faces before they board flights. U.S. Customs has been using biometrics to track entrants to the U.S.

But the practice has drawn scrutiny from privacy advocates and civil libertarians who are concerned about the accuracy and potential misuse of the data being collected. While Congress has called for such systems, others worry that the U.S. is investing billions in a program that may not necessarily keep the nation safer.

Airlines like Delta are betting the convenience of a system that eliminates passports and drivers’ licenses will outweigh travelers’ privacy concerns.

U.S. Customs Commissioner Kevin McAleenan said biometric technology in place at Los Angeles International Airport has helped planes board more quickly. For example, officials were able to load an A380 with more than 350 passengers in less than 20 minutes – half the time it would normally take, he said.