That dog still ain't barking!

On 9-11, with an unknown number of planes flying across the country crashing into buildings, with the President's presence at Booker Elementary announced in the media three days before, and an airport just four miles away, how did the United States Secret Service Protective Detail know for a fact that they did not need to throw President Bush into his armored limousine and start driving in any direction to foil an inbound threat? How did the United States Secret Service Protective Detail know for a fact that by keeping all those kids in that same room with Bush, that they were not risking their lives with a potential inbound jet? How did the United States Secret Service Protective Detail know for a fact that President Bush was safe where he sat, reading about goats, waiting for his speech?