Gee, that really narrows it down, doesn't it? A huge attack, but no mention of how it might take place or when. Put the country on alert (for something that might happen sometime, maybe). Yeah, that'll work. Right.

In perfect 20-20 hindsight, it was obvious what they were planning but not at the time. Even if someone had linked the threat of a huge attack with the report of flight training, there are on average several thousand airline flights a day in the US alone. What could they have done in advance within the constraints of the regulations (e.g. boxcutters being allowed on planes) known at the time?