From this article:

Authorities raised the terrorist threat assessment over the weekend after new intelligence indicated that operatives of Osama bin Laden’s al-Qaida terror network, possibly trained and licensed to fly passenger jets, may now be pilots for some foreign airlines, ideally positioning them to carry out suicide attacks, U.S. officials told NBC News on Monday.

Reinforced cockpit doors intended to thwart hijackers after the Sept. 11, 2001, terrorist attacks would now protect any terrorist pilot at the controls, the officials said on condition of anonymity.

Whoa. While this may not be as easy to pull of in America, getting a ringer into an Arabic airline company would not be all that hard, would it?

A takeover of the airplane by the pilot would leave the passengers in a very bad position: One cell phone call away from an air-to-air missile.

The rest of the article is interesting, too. The "dirty bomb" is fascinating, since almost every expert says that the actual effects of the radiation would not be that serious, but people would go nuts over it anyway due to the brainwashing they have been subjected to about Evil Radiation. The Boogeyman Bomb.