Sep 10, 2011

Clearing the skies on September 11, 2001

A lot of people will be writing about the events of September 11, 2001 today, and all of them will probably be much more well researched and thought out than this little web posting.  Most people that I know have a much firmer grasp on world events than I do, and will undoubtedly dissect what we did, what we should have done, why we must never forget, and so forth.

As a matter of fact, I am sure it will be talked to death, until most everybody is sick of hearing it.

But I wanted to touch on a different event that happened that I may have just a bit more knowledge about than most.  That was the unprecedented order to clear the airspace over the United States for the first time in history.  Some of you may know that I was in the Navy right after high school, and my job among others was as an Anti-Submarine air controller.  So I have a bit of practical knowledge about how difficult it is to keep machines traveling at high rates of speed from bumping into each other.

After the second jet hit the trade center, people in the control centers and towers started getting an idea that this wasn't just a highjacking.  Everybody was getting little bits of information, and some of the planes up in the air started receiving bits of information over cockpit printouts.

Highjack warnings... Terrorist alerts... Lock down your flight decks were some of the cryptic readouts, but nobody had the whole situation.

At the FAA's command center, managers can think of only one way to stop them. Minutes after another jet smashes into the Pentagon at 9:38 a.m., the managers issue an unprecedented order to the nation's air traffic controllers:

Empty the skies.

Land every flight.


Nobody has ever planned for this.  There isn't a procedure for it, let alone a hint of how to accomplish it.  An air traffic control system can sometimes be overwhelmed by just a storm front that everyone has to steer around, but this?  this seems impossible.

Almost 4,500 planes will have to land within hours, many at airports hundreds of miles from where they were headed. Rerouting so many flights seems a logistical nightmare with no margin for error. 

And no one knows how many terrorists might still be in the air. During these hours, those who run the nation's aviation system will come to believe as many as 11 flights have been hijacked.

The first call comes from American flight 11, via a flight attendant who can't reach her cockpit crew.  The local controllers aren't sure what to make of this and check to make sure there is even a flight attendant by her name on board.  There is, and then after that the controllers hear a strange accent through an open mike aboard the aircraft. "We have some planes," he says "Just stay quiet and you will be OK."

At the FAA command center in Herndon, they here the transmission.  "We have some planes", but everybody listening doesn't know how many or for what.

Flight 11 is now off the air, but is descending into New York, Not into JFK or LaGuardia or Newark International Airport but into the city itself.  At Newark's tower, just across the Hudson River from Manhattan, controller Rick Tepper, 41, stands at a console behind a group of other controllers. he sees flames shooting up from the world trade center, but doesn't know what caused it.  He immediately asks everyone in the room, "Did you loose anybody" a number of times. Then the shout line (a sort of hot line for controllers in the region) rings.  He picks it up and the new york center says we lost an aircraft over Manhattan, can you see it?  He answers no, but the trade center is on fire.

At United Airlines headquarters outside Chicago, Andy Studdert rushes to the airline's crisis center, a windowless room with a large screen on one wall. To those who work there, the room resembles the bridge on the Starship Enterprise. "This is not a drill!" he shouts, but the staff already knows.  The team there tells him even worse news, controllers have lost radio contact with a second flight - a United jet that, like American Flight 11, took off from Boston bound for Las Angeles. On the giant screen at the front of the room, airline workers can only watch as United Flight 175, northwest of New York, heads toward Manhattan. Then it disappears.

In the Newark tower, the shout line rings again.

Where's United Flight 175? "Can you see him out the window?" the caller asks Tepper, the Newark controller.

Beyond the New Jersey shipyards, Tepper spots the jet flying north, up the Hudson River. His eyes track it toward the Manhattan skyline. It's moving fast. Too fast. And rocking. Its nose points down in a dive and now it's banking left and then right and moving as Tepper has never seen a jet move and then it starts to level and ....

"Oh my God! He just hit the building," Tepper tells the caller.

At that point, these two men declare ATC zero, which means clear the skies.  In the past that meant have everyone orbit while we figure out a technical glitch, now it means land everything.

At the FAA's command center in Herndon, attention shifts from the weather maps and the radar displays to a new focus, a dry-erase board propped at the front of the room. On it, staffers have begun to scribble the call letters of every flight that controllers around the nation fear might be in the hands of hijackers. People from every discipline are called into the room to help sort things out, from weather specialists to backup air controllers.  Everyone is listening in a phone calls, and more importantly, radio traffic.  There are a few key calls that a pilot can make when under duress that mean something to the controllers.  And all ears are tuned for even the slightest sound of a pilot that just doesn't seem right.

The first step that is taken is ground all aircraft that were preparing to take off.  Anything that wasn't in the air went back to the gate, or back to the garage if it was cargo.  Nothing had permission to take off. 

It is 9:25 AM, and there are 4,452 aircraft in the air.

Over land, the job start immediately.  You can see everybody on radar, and talk to them.  But the New York controllers face a different task.  Their concern lies with the huge number of aircraft that have already left Europe and are heading to the east coast.  they are out of radar range, and voice communications with them is never certain.  HF radio is highly unreliable, and most of the time positions of those aircraft are estimated.

Then American Flight 77 fails to respond.  A report comes from a controller at Washington Dulles International Airport. She has a jet on radar, heading toward Washington and without a transponder signal to identify it. It's flying fast, she says: almost 500 mph.

The FAA warns the Secret Service. Fighter jets from Langley Air Force Base in Virginia race toward Washington. They won't get there in time. The jet has hit the Pentagon. The time: 9:38 a.m.

The FAA widens the order now, anything that can fly, commercial, private, piper cub or helicopter is ordered to the ground.

9:45 a.m.: 3,949 planes in the air.

Pilots are all starting to take the situation serious. Aboard United Flight 890 over the Pacific, Capt. Hosking and another pilot, Doug Price, wait anxiously for news. The message about the hijackings arrived only minutes ago, but the two already have decided: Hijackers are aboard their flight. Quickly, they wedge their bags between a jump seat and the flimsy cockpit door. The door opens inward and, with the suitcases there, no one can budge it. Not without a lot of effort.

And if someone does manage to get through the cockpit door?

Price will be waiting as Hosking flies the jet. He has the cockpit's hatchet-sized crash ax in hand, along with orders to use it.

"If someone tries to come in that door, I don't want you to hurt him," Hosking says. "Kill him."

At the Federal Aviation Administration's command center in Herndon, Va., Delta Flight 1989 joins a growing list of suspicious jets. Some of their flight numbers will be scrawled on a white dry-erase board throughout the morning. Eventually, the list will grow to 11.

During the frantic hours after the order to ground the fleet is issued, controllers will reroute at least 1,300 flights. They will land 48 planes, on average, each minute. Another hijacked jet will crash in Pennsylvania after passengers fight terrorists who took over the jet. A SWAT team will await the landing of another.

9:45 a.m. ET: 3,949 planes in the air.

Aboard American Flight 71, now over Greenland, the captain tells flight attendants to gather steak knives from first class. The knives seem hopelessly inadequate, especially if hijackers have guns, but what choice do they have? They were headed to Chicago, but are now diverted to Toronto.

9:55 a.m. : 3,520 planes in the air.

From aboard United Flight 93, a handful of passengers contact family and friends by cell phone. What they learn - that three jets have already been hijacked and crashed into buildings - will prompt one of the most heroic efforts of the day. Within moments, they will rush the cockpit to try to regain control of the jet.

10:05 a.m. : 2,985 planes in the air.

At United Airline's crisis center, a solitary blip glows red on a big screen. it is United Flight 93 with Air Force jets approaching it rapidly.  What will they do?  order it shot down if it doesn't answer?  A black column of smoke rises from a field due south of the airport, near the town of Shanksville as the Air Force jets arrive.  Nobody had to make that decision.

10:30 a.m. : 1,505 planes in the air.

Halifax in Nova Scotia is a relatively small airport, but has a runway that is jumbo rated, meaning it can handle the large aircraft coming from over the Atlantic.  It is the first airport that can be used by an aircraft coming from that direction, and as such start receiving more traffic than anybody had possible imagined. The orders were simple, land and taxi as far away from the terminal as possible to make room for others, then shut down.  We will come and get you when we can.   It is one of the true good stories that came out of that day, as people from the town volunteered to come out, pick up passengers and take them to their homes, because the airport was overwhelmed with passengers.

10:45 a.m. : 1,081 planes in the air.

At O'Hare in Chicago, workers stand ready to set up 2,000 cots set aside for travelers stranded during snowstorms. Outside, along the airport's edges, O'Hare's 187 snowplows are deployed as roadblocks. They encircle the base of the control tower, their blades pointed toward anything that might approach.

11 a.m. : 923 planes in the air.

Throughout the morning, the FAA slowly checks off the list of suspicious aircraft one by one.  The Herndon command center for once reports good news. Every commercial flight in U.S. airspace - about a quarter of the planes still in the air - is within 40 miles of its destination. The others are still over the oceans, and many are heading toward Canada. But at least all the flights over the United States are accounted for and complying with controllers.

11:30 a.m. : 758 planes in the air.

Then a report comes in from Georgia of a serious car accident.  The pilot of a rescue helicopter is begging for permission to pick up someone who is critically injured. All morning they have refused to make exceptions, even  ordering an aircraft with Attorney General John Ashcroft, who was heading to Washington, to land. Permission is given to launch the helicopter, they decide there has been enough death this day.

Noon : 669 planes in the air.

There are a couple of things that helped on this morning, one was that the skies across the entire USA were nearly clear of any kind of weather.  The second is that the events took place early enough that the west coast traffic had yet to really begin to take to the skies. 

On a normal day, about 20 aircraft each hour are rerouted to new destinations because of emergencies or bad weather. On Sept. 11, controllers rerouted more than 1,100 flights in the first 15 minutes after the order to land the fleet was issued at 9:45 a.m. — more than one every second.

In all, about 3,300 commercial and 1,200 private planes were ordered to land by U.S. and Canadian authorities that day. Almost 75% of those planes landed within just 60 minutes of the 9:45 order. Canadian controllers and airport managers cleared space in small airports north of the U.S. border for 252 jets arriving from Europe and Asia.

In his patch of airspace east of Los Angeles that morning, controller Brian Carver faced a typical dilemma.

One of the biggest airports in the country lay just a few miles away, but landings there were halted for security at the same time the FAA ordered the planes grounded. Carver put several flights into holding patterns. Soon, he found, all the area's smaller airports became overwhelmed by the unexpected traffic.

Within minutes, air traffic officials reconsidered the order closing the airport. Considering the airport's four long runways, the move made sense. Ten minutes later, Carver had redirected the flights and his airspace was empty.

At many big airports, such as Boston, Chicago, Atlanta and Dallas, controllers followed a similar strategy: Let the closest planes headed to those airports land there, even if they passed over smaller airports. Redirecting more than a few of those flights would have taken longer than simply allowing jets to continue. This strategy allowed hundreds of aircraft to land within minutes.

For hundreds of other aircraft, it didn't prove nearly so simple.

Over the Mississippi River valley between Tennessee and Arkansas — a busy corridor in the nation's midsection — controllers at Memphis Center were saturated. Memphis Center is an air traffic facility that handles mostly long-range flights passing through, rather than bound for, that area.

Controllers at the center, used to making sure that flights are on their proper course, suddenly had to redirect more than 100 jets to area airports.  As a result, one of the controllers' few options was to land jets at Memphis International Airport. Luckily, it has a lot of unused capacity. The airport is a bustling FedEx hub at night but relatively quiet during the day. Controllers rerouted 45 jets there, more than double the normal arrivals for that time of the morning.  But one thing Memphis has is ground space, and they used it all up.

Despite occasional confusion and problems throughout the day, controllers never once reported bringing planes too close together.

In all, 2,868 planes landed during the hour from 9:45 a.m., when the order to land all the planes went out, to 10:45 a.m.

During that same time, United landed 154 jets, about 83% of its flights in the air at 9:45 a.m. American landed 169 of its planes, or about 73%.

By 12:16 p.m., U.S. airspace was clear except for military and emergency flights. Only a few transoceanic flights were still landing in Canada.

In the months that followed, the FAA beefed up communications and mandated swifter reporting of any suspicious activity by aircraft.

Officials decided not to write a new set of procedures for clearing the skies. They started to but scrapped the idea. They concluded that the FAA was better off relying on the judgment of its controllers and managers.

"A lot of things were done intuitively, things that you can't write down in a textbook or you can't train somebody to do," said Frank Hatfield, the FAA's eastern region chief.

A lot of people did their jobs very, very well that day.

If you want some more information or graphics, this is a nice resource:

Lots of resources went into this, USA today, Discovery Channel, and the report on ATC activities released by the FAA.


  1. Amazing. 4,452 aircraft in the air and all rerouted and landed without once accident. This was fascinating, and a testimony to the dedication of air traffic controllers. Several of our friends work are controllers in the Twin Cities area, and a lot changed for them on that day.

  2. That is amazing! People make jokes about air traffic controllers but that had to have been nightmarish.

    Thanks for this, SkyDad!

  3. Jeez. I never really stopped to think about what a huge task it was to clear the skies. It's amazing they did it so quickly without crashing any planes into each other.

    This is AWESOME, SkyDad!!

  4. So interesting. I think the whole thing, now that everyone has a timeline of everything that happened that day, after people have figured it out, it is interesting to know that most people did act on instinct, and did what they thought should be done... because no one had the whole picture early on. The air traffic controllers did an amazing job!!!

    (My sister used to live in Nova Scotia and she said that when she heard that people who letting people fom the planes into their homes, it wasnt surprising because that is how people are in NS.)

  5. Amazing, truly. Even on the day when the news stations said the skies were being cleared I thought, how is that even POSSIBLE? That's thousands of flights! I remember reading about people in Gander getting a startling number of jets at their little airport and also housing passengers till things were working again. I think they all did an astounding job the people who land those planes. What a feat! I also bet they all went home after and did strong shots. :)

  6. Thank you for sharing that. It's nice to know that something worked right that awful day.

  7. That was an amazing feat. x

  8. Chris, you hear so much about what went wrong that day, you don't often hear about so much that went right. Thank you for the details I'm just finding out about now, 12 years later. xoxo, Nancy (cause you probably won't recognize my silly old blog name!)

    1. Nancy! I never even knew you blogged!