On his first day as national operations manager at the US Federal Aviation Administration, Ben Sliney made the unprecedented decision to shut down America’s airspace as the country came under attack.
Working from the FAA command centre in Herndon, Virginia, on September 11, 2001, the veteran air traffic controller ordered aircraft on the ground to remain there and told planes already in the sky to land at the nearest suitable airport.
The order came as controllers struggled to track hijacked aircraft and reports emerged that a plane had struck the Pentagon. It would become the first complete closure of US civilian airspace in the nation’s history.
Sliney had not been expected to face a national catastrophe on his first morning in the job. He had returned to the FAA after years working as a lawyer, having previously served as an air traffic controller at major New York airports including JFK, LaGuardia and Newark.
He had joined the US Air Force after leaving high school and worked in air traffic control before serving in Vietnam. After returning to civilian life, he began a long and sometimes interrupted career with the FAA, repeatedly moving between aviation and the law.
In 1981, when President Ronald Reagan dismissed about 11,000 striking air traffic controllers, Sliney was working as a supervisor. With the FAA suddenly short of staff, he returned to active control duties before leaving the agency and representing some of the dismissed controllers as a lawyer.
He eventually came back to the FAA once again. In 2001, an old colleague persuaded him to take a post at the command centre near Washington, where controllers regulated the flow of aircraft across the United States.
After two months learning the centre’s systems and procedures, Sliney was appointed national operations manager. September 11 was his first official day in charge.
The decision to ground every aircraft
The morning began with a routine management briefing. That changed when staff reported that American Airlines Flight 11, travelling from Boston to Los Angeles, had been hijacked.
At first, the incident was treated as a serious but familiar aviation emergency. The United States had not experienced a hijacking for many years, but procedures existed for tracking a suspect aircraft and seeking military assistance if required.
Then reports indicated that a flight attendant had been stabbed. The aircraft’s transponder was switched off and controllers lost its confirmed radar position in north-western Massachusetts.
As Sliney’s team tried to determine where the aircraft had gone, television pictures showed a huge passenger jet crashing into the World Trade Center’s North Tower in New York at 8.46am.
The scale of the impact immediately suggested that this was not an accident involving a small aircraft. Sliney feared the hijacked American Airlines jet had been used as a weapon, although the full picture was still unclear inside the command centre.
Minutes later, United Airlines Flight 175 turned towards Manhattan and struck the South Tower. The possibility that several aircraft were being used in a coordinated attack was now unmistakable.
Sliney first imposed a ground stop on flights bound for New York or passing through New York-controlled airspace. The National Park Service records that he then ordered a nationwide ground stop at about 9.25am, preventing any further aircraft from taking off in the United States.
After the Pentagon was hit at 9.37am, Sliney instructed FAA facilities to direct all aircraft to land at the nearest airport as soon as practicable. The order applied regardless of where planes had come from or where they had been heading.
At the time, about 4,500 commercial, private, military and other aircraft were in US airspace. More than 2,000 were passenger or cargo aircraft, while the remainder included business jets, charter flights and general aviation.
Aircraft abroad that had not yet entered US airspace were prevented from landing in the country. Many were diverted to Canada, Mexico, the Caribbean and countries in Central and South America.
The FAA later recorded that roughly 4,500 aircraft were brought down safely. The agency has described the ground stop as the first complete shutdown of US air traffic and one of the defining operational decisions of the attacks.
The order was effectively an emergency transfer of control from civilian aviation authorities to the military. It reflected Cold War contingency planning known as SCATANA, or Security Control of Air Traffic and Air Navigation Aids, although Sliney did not use the term when he issued the instructions.
Within minutes, officials at FAA headquarters questioned who had authorised the decision. Sliney’s response, according to accounts of the command centre’s actions, was that he had done so because it was necessary.
United 93 and the empty skies
As aircraft began landing across the country, controllers were told to report immediately if any plane failed to follow instructions or made an unexplained change in altitude or direction.
United Airlines Flight 93 had initially followed its planned route westwards. It was later hijacked over Ohio, turned south and then headed back east towards Washington.
The aircraft’s transponder was switched off, forcing controllers to track it using primary radar and reports from other aircraft. Passengers and crew eventually fought back against the hijackers, and Flight 93 crashed into a field near Shanksville, Pennsylvania, at 10.03am.
By then, the skies over the United States had been transformed. The dense pattern of civilian aircraft that had filled radar screens that morning had largely disappeared, leaving only military, police, medical and other authorised flights.
Sliney’s decision was later overshadowed in some public accounts by the role of senior political officials, including Transportation Secretary Norman Mineta. But the 9/11 Commission identified Sliney as the FAA manager who ordered all aircraft to land at the nearest airport.
In the years that followed, his actions were revisited in inquiries, documentaries and the 2006 film United 93, in which he played himself. His first day in the job became inseparable from the moment America’s civilian airspace went silent.
