Greenwald is really pushing this and I think we can go all the way on the back of it. And he was kind enough to link to the Yemen Hub timeline at the History Commons.

IMHO Mukasey is garbling it and the call must have been relayed via Yemen from Afghanistan to the US.

The key questions about the Yemen hub include:
(1) How many calls from/to the hijackers did the NSA intercept?
(2) What was said in them? We want recordings, transcripts, and contemporary NSA reporting.
(3) How many of the calls were received when the hijackers were already in the US?
(4) KEY QUESTION: why didn't the NSA inform the FBI of the calls to the US?
(5) How many times in the relevant period did the NSA tip the FBI off about calls from other suspected terrorists overseas to the US?
(6) Did the NSA's inspector general write a report about the NSA's performance pre-9/11? Give it to me.
(7) What was the terrorist plot Alhazmi and Almihdhar were overheard discussing in early 2000?
(8) What other calls to the hijackers did the NSA intercept?
(9) Why have an entire raft of administration officials (Bush, Cheney, Haden, McConnell and now Mukasey) falsely claimed the NSA could not have actually passed the information to the FBI under FISA? This false claim is the only justification for the NSA's wiretapping programme?

I could probably think of more, but that will do for now.