Tuesday, 04 January, 2005

9/11: Why weren't the planes shot down?

The first chapter of the 9/11 Commission Report gives a very detailed account of what we know occurred before the hijackers boarded the airplanes, the events that unfolded on the airplanes, and the responses of the different corporate and government agencies that were involved.  Our understanding of when the individual flights were hijacked is based on several things:  unguarded transmissions from the airplanes by the hijackers (who apparently thought they were communicating with the passengers), transponder data or lack thereof due to the transponders being turned off, radar records showing course deviations, lack of response to instructions by FAA controllers, and communications from flight attendents and passengers to people on the ground.  In addition, we have varying degrees of detail about happenings aboard from those cabin-to-ground communications.  Finally, the cockpit voice recorder and flight data recorders that survived the crash of Flight 93 in Pennsylvania provide some additional insight.

A look at the timeline of events answers one of the biggest questions I've heard expressed about the events of the day:  Why didn't the military do anything about it?  The simple answer is that there wasn't enough time between the flights' being taken over and the crashes for controllers to determine that the flights were hijacked, and for that information to be communicated to people responsible for deciding what to do about it.  For example, American Airlines Flight 11 departed Boston at 7:59 A.M.  The last routine radio transmission occurred fifteen minutes later at 8:14, and takeover occurred within minutes after that.  At 8:19, a flight attendant notified American Airlines of the highjacking by making a call from one of the seat phones in the rear cabin.  Boston Center learned of the hijacking five minutes later.  At 8:38, Boston Center notified the military, which scrambled fighters at 8:46--less than a minute before Flight 11 crashed into the North Tower of the World Trade Center.

United Flight 175 took off from Boston at 8:14--the same time Flight 11 was being taken over.  Flight 175 was taken over sometime between 8:42 and 8:46 while controllers and others were trying to figure out what to do about Flight 11.  The first indication of anything wrong with Flight 175 was at 8:47, when the transponder code was changed.  A flight attendant notified United of the hijacking at 8:52.  It crashed into the South Tower at 9:03.

Thirty two minutes (the time between likely takeover and crash of Flight 11) is an astonishingly short amount of time for information to flow from controllers to decision makers to alert fighter crews who then have to scramble and find an aircraft.  Otis Air Force Base where the fighters were based, is 153 miles from New York City.  At the F-15's maximum published speed of 1,650 MPH, it would take almost six minutes to cover that distance.  Obviously they had no chance to stop Flight 11 which crashed just as the fighters were taking off.  It's possible, although highly unlikely, that they could have located and engaged Flight 175 before it crashed at 9:03.  In addition, it's unlikely that anybody would have given the order to shoot down a domestic passenger aircraft over a major metropolitan area, especially with less than 15 minutes in which to make that decision.

American Flight 77, which departed Washington Dulles at 8:20 is a somewhat different story.  It was taken over sometime between 8:51 and 8:54, when it made an unauthorized turn to the south.  The transponder was turned off at 8:56, making the aircraft very difficult to identify on radar.  Although American Airlines was aware at 9:05 that the flight was hijacked, there is no indication that the FAA knew about the hijacking.  The FAA did learn that the flight was "missing," and notified the military of it at 9:34.  A National Guard C-130 that had just taken off for Minnesota saw the aircraft, identified it as a Boeing 757, and began to follow.  Three minutes later, Flight 77 crashed into the Pentagon.  There were fighters in the air near Washington, but due to the mass confusion caused by the first two crashes, they were looking in the wrong place for the wrong thing.  And again, it's doubtful that they would have engaged the airplane over metropolitan Washington.

In my opinion, the only reason the hijackers didn't go four for four was that United Flight 93 was 25 minutes late departing.  It didn't leave the ground until 8:42.  The pilots actually received a warning about increasing cockpit security just minutes before the flight was taken over.  The passengers ultimately revolted and attempted to retake the airplane after learning of the first two hijackings and crashes.  Had the passengers not revolted, it's unlikely that the military could have located Flight 93 and received authorization to shoot it down in time to prevent it from striking its target (likely the Capitol or the White House).  There's no doubt in my mind that the hijackers would have been successful had the flight departed on time from Newark.

At the time of the hijackings, our nation's air defense was designed to repel a military attack from outside.  There hadn't been a domestic hijacking in over 10 years, and in any case a hijacked aircraft wasn't considered a dangerous weapon.  As the 9/11 Commission Report states:

NORAD and the FAA were unprepared for the type of attacks launched against the United States on September 11, 2001.  They struggled, under difficult circumstances, to improvise a homeland defense against an unprecedented challenge that had never before encountered and had never trained to meet.

This is a common theme throughout the Report:  al Qaeda studied our defenses, identified our weaknesses, and exploited them to the fullest advantage.  More later.