By Don Phillips
The Washington Post
WASHINGTON — Controllers watching their radar screens at Washington, D.C.’s Dulles International Airport spotted an unidentified aircraft flying at unusually high speed directly toward the White House early Tuesday morning, and warned authorities minutes before the Boeing 757 turned tightly and circled around to slam into the Pentagon, according to federal aviation sources.
The controllers couldn’t identify the plane because someone on board apparently had turned off its transponder, the equipment that sends the plane’s airline, flight number, speed and altitude to radar screens. Tentatively, the plane was identified as American Flight 77, which had been scheduled to take off from Dulles at 8:10 a.m. for Los Angeles, with two pilots, four flight attendants and 58 passengers on board.
The skill with which the plane was flown, including the knowledge of how to turn off the transponder, raised the probability that a trained pilot was at the controls, possibly a hijacker.
Sources were not specific about the times of the events, but said that after leaving Dulles the plane continued west for a while. At some point, apparently after turning off the transponder, the plane turned back toward Washington with no radio contact.
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, D.C.’s Reagan National Airport and much of Washington, D.C., 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. They called controllers at National Airport to tell them an unidentified unauthorized aircraft was headed their way.
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 a.m., less than an hour after two other aircraft hit the World Trade Center towers in New York City.
Federal aviation rules limit the speeds of commercial aircraft flying below 10,000 feet. The sources said it appeared this plane was at full throttle.
Controllers then saw that a Boeing 757 identified as United Flight 93, flying from Newark to San Francisco, had turned toward Washington, D.C., over Pennsylvania. But the United plane crashed for unknown reasons about 10 a.m. about 80 miles southeast of Pittsburgh.
Federal aviation officials are reporting that the transponders had been turned off on all four planes that crashed Tuesday, including two that flew into the World Trade Center in New York City.