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
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
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
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,
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
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
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
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,''
Over the oceans, the hurdles to rerouting
flights were more substantial: no radar, poor
communication and no runways for thousands of
Instead of radioing flights directly,
controllers handling ocean traffic must send text
messages through a private firm that relays them
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
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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