Meanwhile, the Justice Department says at least one hijacker on each of the four planes in Tuesday’s attacks was trained at a U.S. flight school. Overall, 50 people may have been involved in the hijackers’ well-financed operation. Justice Department spokeswoman Mindy Tucker said yesterday both cash and credit cards were used by the hijackers to purchase tickets, hotel rooms and other things. The FBI’s massive investigation stretches from the Canadian border to Florida, where some of the participants learned how to fly commercial planes before the attacks. Tucker said flight schools in more than one state were involved in the training of the hijackers, several of whom had pilot’s licenses.