On a recent morning, passengers boarding Emirates flight 232 from Washington Dulles airport to Dubai confronted an unfamiliar sight: a uniformed Customs and Border Protection officer at the gate.

Before passengers approached the airline gate agent, the customs officer, Sung Hyun Ha, scanned their travel documents at a kiosk, which was also equipped with a camera. The photograph taken was matched against a facial scan that foreign visitors submitted to Customs and Border Protection when they entered the country or from their visa application, while the passenger’s identification also was checked against law enforcement and intelligence databases.

The pilot effort is part of a decades-long push to more accurately identify people who overstay their visas and remain in the United States, a group that represents the largest number of people in the United States illegally.

The department believes that if officials can better track who has left the country, they will be able to better assess who has stayed here beyond the legal limit of their visa.