The mailing gave Mohamed Atta pilot status.

On the six-month anniversary of the Sept. 11 terrorist attacks, the Venice, Fla., flight school that trained two of the airplane hijackers received new immigration visas changing their legal status from tourists to student pilots.

The owner of Huffman Aviation International expressed surprise after getting the visa-approval notifications in Monday's mail from the Immigration and Naturalization Service.

The visas were for Mohamed Atta and Marwan al-Shehhi, who commandeered and then piloted two jetliners into New York City's World Trade Center. The documents formalized their INS status as nonresident student pilots.

INS officials conceded Tuesday that the long-after-the-fact mailing, which bore a March 5 postmark, was embarrassing. Since the terrorist attacks, the agency has been criticized for not adequately screening foreign nationals who come to the United States to visit, study or work.

''It's regrettable that the flight school is receiving the paperwork on this late date,'' said Russ Bergeron, the INS spokesman in Washington.

``The important thing to recognize is the decisions to change their status were made . . . before Sept. 11, and at the time there was no information made available to INS regarding these people and their link to terrorism.''

INS officials said the episode was caused by a backlog in data entry of the visa notifications. Though the two applications were approved last summer, the delay held up the mailing to the school until last week.

Bergeron said the data entry and mailing were done by an outside contractor, Affiliated Computer Services. The London, Ky., company was hired to reduce the backlog of typing written notifications into the agency's databases.

Bergeron said the notification received by the flight school was the second one sent out. He said INS had already advised Atta and al-Shehhi their visa applications were accepted weeks before Sept. 11.

The problem arose because INS never thought about contacting ACS and telling them not to proceed with the mailing -- because Atta and al-Shehhi were dead.

Atta's visa change was approved July 17, 2001, and al-Shehhi's on Aug. 9, 2001, according to copies of the notifications obtained by The Herald.

Rudi Dekkers, owner and president of Huffman Aviation, said Atta and al-Shehhi completed paperwork on the the M-1 nonimmigrant student visas on Aug. 29, 2000, just before they began a six-month flight instruction program at the school.

According to travel records obtained by The Herald shortly after the attacks, the hijackers first entered the country on multiple-entry tourist visas -- al-Shehhi on May 29, 2000, and Atta on June 3, 2000.

About six months later, when Atta was returning from a trip to Madrid on Jan. 10, 2001, INS inspectors at Miami International Airport became suspicious after he mentioned taking flight lessons on the tourist visa.

It was not illegal for foreign nationals to take flight lessons while using a tourist visa. But immigration officials prefer immigrants who are studying in the United States to have student visas.

After interrogating him, inspectors decided not to detain Atta because he had applied for the student visa.

There is no record that al-Shehhi was also questioned about his tourist visa.

In their student visa notifications, both men were cleared to stay in the United States until Oct. 1, 2001. The men completed their flight course on Jan. 3, 2001 -- more than six months before their visas were approved.

On Tuesday, Rep. John Conyers, D-Mich., criticized the visa notification episode.

''I am astonished that while the INS is fixated on detaining and rounding up countless Arab Americans without any justification, it has failed to take basic steps to ensure that visas are not issued to known terrorists,'' he said.

Dekkers said the forms vindicated that his school did not break the law.

''What is odd to me is that the visas were approved six months after they left,'' Dekkers said. ``When they hit the buildings, they were approved to be here.''

This report was supplemented with material from The Associated Press.