Amid criticism of the use of facial scans on travelers by the federal government, U.S. Customs and Border Protection and Delta Air Lines are continuing testing of facial scans at Hartsfield-Jackson International Airport.

Atlanta-based Delta this month launched a test using facial recognition for boarding at two gates on Concourse E at Hartsfield-Jackson International Airport. The test at gates E10 and E12 allowed customers flying to Paris to opt in to participate in the test, which involves approaching a camera while their picture is taken, before getting a confirmation receipt and boarding.

Delta said the test “will also allow agents to more easily engage with customers during the boarding process.”

The test was suspended briefly during Delta's recovery from the power outage at Hartsfield-Jackson on Dec. 17, but resumed Dec. 19.

Plans are to expand the test to more daily flights.

However, a report released last week by Georgetown Law's Center on Privacy and Technology said testing of facial scans is being done at airports without certain legal and technical safeguards, while U.S. Sens. Ed Markey, D-Mass., and Mike Lee, R-Utah, wrote a letter to the U.S. Department of Homeland Security raising concerns about the issue.

“When American citizens travel by air internationally, they should not have to choose between privacy and security,” Markey said in a written statement.

Facial recognition boarding is one of a number of tests Delta is working with Customs and Border Protection (CBP) on, including facial recognition technology used for exit screening at gates F6 and F9 at Hartsfield-Jackson since last year and other facial recognition tests at New York's John F. Kennedy International Airport and at the Concourse E gates in Atlanta. The exit screening technology is designed to give CBP "enhanced ability to record when visitors depart the U.S.," and all customer data is "securely managed by CBP," according to Delta.

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AJC Business reporter Kelly Yamanouchi keeps you updated on the latest news about Hartsfield-Jackson International Airport, Delta Air Lines and the airline industry in metro Atlanta and beyond. You'll find more on myAJC.com, including these stories:

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Atlanta-based Delta Air Lines, the only remaining U.S. passenger airline to fly the 747, is retiring the plane from its fleet. In 1966, Boeing announced plans to build the 747. In 1969, the Boeing 747-100 made its first flight. The 747's distinctive "hump" could be used as a first-class lounge, extra seating or as cargo space. Atlanta-based Delta Air Lines first operated the 747 in the 1970s. In this Oct. 1970 photo, a Delta crew gets set to take off on a pre-inaugural flight over north Georgia. As far