At least one hijacker on each of the four planes in Tuesday’s terrorist attacks was trained at a U.S. flight school, the Justice Department has said. Overall, 50 people may have been involved in the hijackers’ well-financed operation. “Both cash and credit cards were used” by the hijackers “to purchase tickets, hotel rooms and other things,” Justice Department spokeswoman Mindy Tucker said Wednesday. U.S. Attorney General John Ashcroft said that 12 to 24 hijackers commandeered the four planes, and a government official said another two dozen or so are believed to have assisted them. About 40 of the men have reportedly been accounted for, including those killed in the suicide attacks, but 10 remain at large, the Los Angeles Times reported Wednesday night on its Web site, citing an unidentified source with knowledge of the investigation. The Times reported that at least one of the suspects receiving advanced flight training in Florida was a commercial pilot from Saudi Arabia. Some of those involved in the plot left suicide notes, but they are not believed to have been the hijackers, a government source told the Associated Press. It’s unclear whether those who left the notes actually killed themselves.