A communication breakdown led French officials to allow a plane to take off for America even though US authorities had asked that it be held during a high-threat terror alert.
The incident, disclosed by Homeland Security Undersecretary Ms Asa Hutchinson in an interview with Associated Press, has helped bring about changes in the way US officials talk to foreign governments during terror threats.
In December, the National Targeting Centre in Virginia had worked for 90 minutes to verify the backgrounds of everyone aboard the jet but still had questions about two or three passengers when it was learned the plane had departed.
US officials worked feverishly to complete their checks, aware of the possibility that a plane carrying hundreds of people could be streaking toward the United States with terrorists aboard.
Long before the jet approached US air space it was determined none of the passengers posed a security risk. But the time it took to clear them was "gut-wrenching," Ms Hutchinson said in the recent interview.
Officials would not name the airline involved nor provide other details.
