Thought Leadership

OFF-TOPIC: 9/11 trivia

By Colin Walls

I recently read a book that I found fascinating: The Only Plane in the Sky: The Oral History of 9/11 by Garrett M. Graff. The story of that fateful day is told by people who were there or very directly touched by the events: survivors from the buildings, emergency service staff, military people, relatives of people who died or survived, witnesses who were nearby. Each chapter provides some of the basic facts and the words of these folks fill in the details. The pace of the book is almost like a thriller – I kept turning the pages.

I was surprised when I realized how long ago this event was. There are many adults around now who were not even born. Everyone remembers where they were when they first heard the news – right? I know that I have a crystal clear memory. In the days and weeks that followed we learned more of the details, but this book took me way beyond what I thought I knew. I hope that my fascination with the details does not make it sound as if I was not shocked and deeply saddened by the suffering, death and destruction that resulted. I assure you that I care, but I am able to stand back and view it as a historical event of global significance that changed all our lives for ever. And I was intrigued to learn so much interesting detail [some of which, if I am frank, is rather trivial]:

  • I have always thought of the World Trade Center as being two buildings – the Twin Towers. However there were actually another 5 structures, including a substantial hotel. They were all destroyed on 9/11.
  • The WTC South Tower was the first sky-scraper ever to collapse [of course, the North Tower was the second].
  • The WTC fires were still burning in early December – 99 days later.
  • The Pentagon is the biggest low-rise office block in the world.
  • The Pentagon not only has 5 sides, but it has 5 stories and the rooms are arranged in 5 “rings”.
  • It was fortunate, and almost definitely accidental, that the segment of the Pentagon hit by the plane was the first one to have been refurbish and this work had only recently been completed. This meant that the damage sustained was somewhat less than otherwise might have been the case, as part of the work was to reinforce the structure against various types of attack; nobody anticipated an impact by an airliner at 400mph. Also, reoccupation of the section was incomplete, so the death toll was mercifully less than had it been full of staff.
  • A Boeing 747 can fly at an altitude of 45,000 feet. At least, if it is modified like Air Force One was. The president was on board and they ascended to protect him, as there was a fear that terrorists might attack the plane. By being so high, they figured that it would be almost impossible for a highjacked plane to reach them and, anyway, they would easily be spotted.
  • As the day progressed and all commercial aircraft were grounded, there were a few planes that did not respond. So there was a fear that there might be a number of other hijacked aircraft. Fortunately, they were gradually accounted for, as the military had been authorized to shoot down any plane that was clearly about to do some harm.
  • It was challenging to keep track of the US air space on that day, as there was very little conventional radar. The systems relied on cooperation from planes to perform air traffic control. All the radar was pointing away from the US, as it had been assumed that any threat would come from outside the country.

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This article first appeared on the Siemens Digital Industries Software blog at