Massoud, the Taliban's sworn enemy in the North of the country, had just been killed by suicide bombers on September 9th. BBC World News were reporting about his murder while the 9/11 attacks were happening. Earlier in the year, he spoke at the EU Parliament and warned the US against Osama Bin Laden.

What I'm trying to say is that there were breadcrumbs in the public arena to make an educated guess the moment the second tower was hit.