Film producer Robert Erickson, working on a documentary for the National Geographic Channel that focuses on the last 24 hours prior to the 9/11 attacks, has encountered roadblocks in trying to find interview subjects--specifically, those who reportedly encountered accused hijackers Mohamed Atta and Abdulaziz Alomari in the Portland, Maine, area on the night and morning of September 10-11, 2001.

As reported in the Portland Press Herald on March 31:

Erickson said he’s also been unsuccessful in tracking down any of the passengers or the two pilots who flew with the terrorists from Portland to Boston on US Airways Flight 5930, a small commuter plane that carried about 10 passengers that morning.

....Similar roadblocks have stymied his efforts in Boston as well, he said.

Erickson said he has filed a request with the FBI through the federal Freedom of Information Act seeking the names of people who encountered the terrorists, such as the maid who cleaned their room at the Comfort Inn and the employees at Walmart, but has not received any response.

“A contributor to the History Commons has obtained a 298-page document entitled Hijackers Timeline (Redacted) from the FBI, subsequent to a Freedom of Information Act request. The document was a major source of information for the 9/11 Commission's final report. Though the commission cited the timeline 52 times in its report, it failed to include some of the document's most important material.

The printed document is dated November 14, 2003, but appears to have been compiled in mid-October 2001 (the most recent date mentioned in it is October 22, 2001), when the FBI was just starting to understand the backgrounds of the hijackers, and it contains almost no information from the CIA, NSA, or other agencies. This raises questions as to why the 9/11 Commission relied so heavily on such an early draft for their information about the hijackers.”

More here:
http://www.cooperativeresearch.org/fbi911timeline
(Local mirror of zip file: 7.8 MB)

Summary of what the FBI document reveals: