On Friday, federal authorities arrested a man in New York in connection with this week’s four airplane hijackings, marking the first big break in a worldwide investigation to find those responsible for the worst terrorist attack on U.S. soil. The man, whose identity was withheld, was taken into custody on a material witness warrant, said Jim Margolin, spokesman for the FBI in New York. The warrant allows authorities to hold someone considered crucial to the investigation without charging him with any crime. A law enforcement source told the Associated Press that the man arrested was the same person detained Thursday at New York’s John F. Kennedy Airport after showing what authorities later said was a pilot’s license issued to his brother. Both Margolin and New York Police Commissioner Bernard Kerik refused to provide any further details on the arrest, says the Associated Press. Court records have been sealed.