Flagg and the former prosecutor, however, said it was the second bag that identified all 19 hijackers.
"That was the one that became the Rosetta stone," Flagg said.
Tracking the hijackers
Luggage left at Portland airport enabled investigators to quickly identify the Sept. 11, 2001 hijackers, including leader Mohamed Atta and conspirator Abdulaziz Alomari.
1. Atta and Alomari check out of a Comfort Inn in Portland, Maine at 5:33 a.m. on Sept. 11, 2001.
2. 5:45 a.m.: They drive to Portland airport, arriving at about 5:45 a.m., for a scheduled flight to Boston.
3. They board a 6 a.m. commuter flight from Portland to Boston's Logan Airport.
4. Atta and Alomari board American Airlines Flight 11, for an 8 a.m. flight from Boston to Los Angeles.
5. Atta, Alomari and others hijack Flight 11 at 8:14 a.m.; they crash it into the World Trade Center's North Tower at 8:46 a.m.
6. Atta's luggage fails to make it onto Flight 11. The bag, left at Portland, contains evidence that helps investigators identify the hijackers.
About the reporter
Michael Dorman, an Opinion editor for Newsday who covered the civil rights movement for the paper in the 1960s, is also the author of 17 books, including "The Secret Service Story" and "The George Wallace Myth."
A mix-up in Boston prevented the luggage from connecting with the plane that hijackers crashed into the north tower of the World Trade Center.
An airport that was the starting point for one of the Sept. 11 hijackers was evacuated for several hours after receiving a bomb threat signed under the alleged terrorist's name.
Mayo was to appear in federal court later Thursday on a charge of interfering with a flight crew after disrupting United 923 as it flew from London to Washington, D.C., on Wednesday.
Instructor testified that instructors at the school breathed "a collective sigh of relief" when Atta and al-Shehhi completed their training and left the school