Do we ever catch terrorists at airport screenings?

It seems like every other week or so we kill Al Qaeda's number two or three leader via a predator drone. Occasionally the FBI rounds up some nuts in suburbia who have intentions of launching some sort of attack on the United States.

Have we ever though stopped a bomber at an airport screening? Have we prevented a terrorist attack by making someone take off their shoes, dump out their water or by seeing a bomb vis a vis a full body scanner?

Seems curious that I can't think of a single instance of the Secretary of Homeland Security (be it Ridge, Chertoff or Napolitano) coming in front of the cameras to announce that a terrorist had been apprehended at the airport thanks to our enhanced screening techniques.