i believe it was louis freeh (spelling?) head of fbi that gave a press conference and stated that the hijackers left 'no paper trail' whatsoever.
he said that given this even their identities cannot be confirmed. (iirc)
now that i think about it maybe a better analogy is half burnt passport that fell from sky to magic jfk bullet.
anyway, given that, how can we follow the money?
------------------
http://www.fbi.gov/congress/congress...ller050802.htm
...
The hijackers also apparently left no paper trail. In our investigation, we have not yet uncovered a single piece of paper –– either here in the U.S. or in the treasure trove of information that has turned up in Afghanistan and elsewhere –– that mentioned any aspect of the September 11th plot. As best we can determine, the actual hijackers had no computers, no laptops, no storage media of any kind. They used hundreds of different pay phones and cell phones, often with prepaid calling cards that are extremely difficult to trace. And they made sure that all the money sent to them to fund their attacks was wired in small amounts to avoid detection.
...