Authorities in the United States have reviewed airport security footage as they continue to investigate how a woman sneaked on board a Delta Air Lines flight from New York to Paris without a ticket last Tuesday –– one of the busiest travel days of the year.

A passenger went through security screening but avoided identity and boarding pass checks before flying out of the United States, a T.S.A. representative said.

Officials say the woman is a Russian national who did not have a ticket when she boarded the plane at John F. Kennedy International Airport.