Much maligned air traffic system came through on 9/11

By Alan Levin
August 13, 2002

On a typical summer day, a thunderstorm somewhere sends air traffic controllers scrambling. Even a small storm can disrupt the meticulous choreography of flights from coast to coast.

Now, imagine violent weather blanketing the entire country. That, in a nutshell, is what the U.S. aviation system faced on Sept. 11 after officials ordered all planes to land.

Never before had the air traffic system responded to so many problems occurring simultaneously. For individual air traffic controllers, the work was chaotic and intense but straightforward: Pick a new route for each flight. Radio instructions to turn. Hold traffic to keep airways from overcrowding.

But collectively, landing nearly 4,500 planes was a massive undertaking and a historic achievement. It required intense cooperation, swift decision-making and the unflinching work of thousands of people. Across the nation, controllers searched for alternate airports to land large jets even as their traumatized colleagues streamed back from break rooms after watching the attacks on TV.

A bit of luck helped, too. The weather across the country was excellent: There were few actual storms to deal with. The attacks occurred before most of the first wave of flights took off on the West Coast. By late afternoon, there would have been as many as 7,500 aircraft aloft.

Yet everyone agrees the system, criticized for years for flight delays and computer problems, performed admirably on Sept. 11.

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.

During the morning, each part of the nation required its own battle plan:

* New York air traffic officials shut down hundreds of miles of airspace almost immediately after the second hijacked jet struck the World Trade Center at 9:03 a.m.

* In several air traffic facilities -- including Boston, where two of the hijacked jets had taken off -- controllers feared their own lives were in danger and evacuated. Despite these fears, all large air traffic facilities resumed operation within an hour and remained open the rest of the day.

* In air traffic centers in Cleveland and Indianapolis, two hijacked jets disappeared from controllers' radarscopes. Controllers were forced to move routine flights out of the way of the hijacked jets and began clearing the skies almost at once.

* At small airports from Arkansas to the Yukon Territory, controllers directed huge jets to land on normally quiet runways.

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.

Memphis was a godsend

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.

To deal with the workload, controllers scrapped the normal air traffic boundaries, controller Richard Anderson said. Instead of handing off a descending jet from one controller to another as it got closer to the airport, a single controller guided a jet until the airport's controllers took over. This eliminated as many as a dozen time-consuming radio calls per flight, simplifying matters for pilots and controllers, Anderson said.

Unlike other air traffic centers, the Memphis Center has few large airports within its boundaries.

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. (Only Indianapolis International Airport received as many.)

But that still wasn't enough. They sent other jets to Little Rock until controllers there telephoned Memphis and said they couldn't handle any more. They directed a few stragglers to Fort Smith Regional Airport in western Arkansas.

''We were just filling up all the airports,'' Anderson said.

Over the oceans, the hurdles to rerouting flights were more substantial: no radar, poor communication and no runways for thousands of miles.

Instead of radioing flights directly, controllers handling ocean traffic must send text messages through a private firm that relays them to pilots.

That process led to at least one close call over the Atlantic Ocean.

About 10:30 a.m., controller Bob Berry discovered that a Virgin Atlantic flight midway over the Atlantic had turned around and was headed east, back toward London. The pilot, running short on fuel, reported he was making the turn but did not wait for approval from controllers.

Berry, based in the same Long Island, N.Y., facility where officials had earlier begun clearing the skies, calculated that the jet was suddenly pointed directly toward a westbound flight that also was at 36,000 feet. They were perhaps 10 minutes from colliding.

Berry sent an urgent order through the private firm for the Virgin jet to descend 1,000 feet. The order reached the jet in time. The Virgin jet descended 1,000 feet, and the two jets passed safely.

Intuition ruled the day

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. 



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