I fly to and from DCA quite frequently, and some of the air marshalls are SO obvious they might as well wear signs on their backs. They are often in seat 1D, for instance. They are always on the plane before anyone else boards. The list goes on and on. No self-respecting graduate of terrorist school would have trouble identifying at least one air marshall. But two or three might be on board -- there were at least three on the infamous US Air flight from PIT -- and that's another matter!

Bruce