9:30 a.m. September 11, 2001: Who Warns Who of Flight 77’s Impending Approach to D.C.?

Chris Stephenson, head flight controller at Washington’s Reagan National Airport tower, says that he is called by the Secret Service around this time. He is told an unidentified aircraft is speeding toward Washington. Stephenson looks at the radarscope and sees Flight 77 about five miles to the west. He looks out the tower window and sees the plane turning to the right and descending. He follows it until it disappears behind a building in nearby Crystal City, Virginia. [USA Today, 8/11/2002] However, according to another account, just before 9:30 a.m., a controller in the same tower has an unidentified plane on radar, “heading toward Washington and without a transponder signal to identify it. It’s flying fast, she says: almost 500 mph. And it’s heading straight for the heart of the city. Could it be American Flight 77? The FAA warns the Secret Service.”
[USA Today, 8/12/2002] In short, it is unclear whether the Secret Service warns the FAA, or vice versa.