Reply #26: The ATC assumed a military plane...

[Bolo Boffin]

...based on the speed of the blip. There's no ATC in that room that thinks they were looking at anything other than Flight 77 now. That's clear from the O'Brien interview.

http://poly.union.rpi.edu/article_view.php3?view=793&pa...

The plane would have appeared on radar screens as an unidentified blip, called a "primary target"—something commonly seen by controllers when an aircraft doesn’t have a transponder or is a military aircraft flying with its transponder turned off. But the airspace around Dulles, Washington Reagan National Airport and much of Washington is designated "class B" airspace, meaning no one is supposed to fly there without a working transponder and permission from a controller.

The sources said Dulles controllers noticed a fast-moving primary target in their airspace east-southeast of the airport, where it shouldn’t be, headed directly toward the restricted airspace around the White House.

But as they watched, the plane began turning to the right away from the White House, circling a full 270 degrees to the right and approaching the Pentagon from the southwest. It then dropped below radar level, disappearing from the controllers’ screens, shortly before hitting the Pentagon about 9:30 am, less than an hour after two other aircraft hit the World Trade Center towers in New York City.

The timing of the primary target was in agreement with the PT being Flight 77. It was flying in the correct trajectory (from SW) to be Flight 77. It's Flight 77.