There was a Dallas to San Francisco flight that was going to be hijacked -- and would have been, had it not been delayed by a cargo-net problem.
I heard this first-hand from a passenger. He said four young, Arab males were pacing and fighting amongst themselves during the delay. When the passengers were released, the four Arabs bolted (The same men were apparently arrested trying to board an Amtrack train in San Antonio a couple of days later).
Looking at the path from DFW to SFO, Sears Tower in Chicago would seem like a likely target.
From what I've read, there were only two arrested in San Antonio: Gul Mohammed Shah a.k.a. Ali Ayub Khan, and Mohammed Jaweed Azmath. They were arrested with box cutters, $5000 in cash, and hair dye; their bodies were apparently shaved. But they got off, charged only with credit card fraud; as I recall, they've both been deported.
So, if the hijacking story is true, why are they not being held in the same manner as Jose Padilla?
[By the way, these two are connected with Mohammed Pervez and possibly with Sabash Gurung. But, as far as I know, those two weren't on the plane.]