PORTLAND (AP) – The final report of the national commission investigating the terrorist attacks of Sept. 11, 2001, did not resolve one question the city’s transportation director would like to see answered.

“Why Portland?” Jeff Monroe said. “That’s the question we’ve been asking for three years.”

The report released Thursday said no physical, documentary or analytical evidence can explain why hijackers Mohammed Atta and Abdulaziz al Omari drove to Portland from Boston on the morning of Sept. 10, only to return to Boston’s Logan Airport on the morning of Sept. 11. after checking in at the jetport for the 6 a.m. flight to Boston.

“Interrogation of detainees has produced no solid explanation for the trip,” one footnote reads.

Commission members rejected theories that the hijackers came to Portland to avoid tight security at a larger airport.

Both men were screened again in Boston, where they also passed through security without incident. The weapons believed to have been used, short-bladed knives, were not banned at the time under security rules in any airport.

Atta “reacted negatively” when informed that he would have to check in again in Boston, an FAA official said, but he successfully passed through security screening.

Commission members had one possible explanation for why the men flew from Portland, the same reason any passenger might pick a departure point – convenience.

“The Portland Jetport was the nearest airport to Boston with a 9/11 flight that would have arrived at Logan in time for the passengers to transfer to American Airlines Flight 11,” the report stated.

Officials have speculated that some hijackers flew from Portland so fewer of them would arrive together in Boston.

“The best hypothesis is that they were going through Boston, and they didn’t want to all show up all at once,” said Monroe.

And although Portland police and the FBI were flooded by reports of sightings of the men in the days after the attacks, the commission found no record of earlier visits to Portland.

AP-ES-07-23-04 0217EDT