9/11

The Attacks

The September 11 attacks (also referred to as 9/11) were a series of four coordinated terrorist attacks by the Islamic terrorist group al-Qaeda on the United States on the morning of Tuesday, September 11, 2001. The attacks killed 2,996 people, injured over 6,000 others, and caused at least $10 billion in property and infrastructure damage and $3 trillion in total costs.

Four passenger airliners operated by two major U.S. passenger air carriers (United Airlines and American Airlines)—all of which departed from airports on the northeastern United States bound for California—were hijacked by 19 al-Qaeda terrorists. Two of the planes, American Airlines Flight 11 and United Airlines Flight 175, were crashed into the North and South towers, respectively, of the World Trade Center complex in New York City. Within an hour and 42 minutes, both 110-story towers collapsed, with debris and the resulting fires causing partial or complete collapse of all other buildings in the World Trade Center complex, including the 47-story 7 World Trade Center tower, as well as significant damage to ten other large surrounding structures. A third plane, American Airlines Flight 77, was crashed into the Pentagon (the headquarters of the United States Department of Defense) in Arlington County, Virginia, leading to a partial collapse of the building’s western side. The fourth plane, United Airlines Flight 93, initially was steered toward Washington, D.C., but crashed into a field in Stonycreek Township near Shanksville, Pennsylvania, after its passengers tried to overcome the hijackers. It was the deadliest incident for firefighters and law enforcement officers in the history of the United States, with 343 and 72 killed respectively.

The Hijackers.
The Hijackers.

Suspicion for the attack quickly fell on al-Qaeda. The United States responded to the attacks by launching the War on Terror and invading Afghanistan to depose the Taliban, which had harbored al-Qaeda. Many countries strengthened their anti-terrorism legislation and expanded the powers of law enforcement and intelligence agencies to prevent terrorist attacks. Although al-Qaeda’s leader, Osama bin Laden, initially denied any involvement, in 2004 he claimed responsibility for the attacks. Al-Qaeda and bin Laden cited U.S. support of Israel, the presence of U.S. troops in Saudi Arabia, and sanctions against Iraq as motives. Having evaded capture for almost a decade, bin Laden was located and killed by SEAL Team Six of the U.S. military in May 2011.

The destruction of the World Trade Center and nearby infrastructure caused serious damage to the economy of Lower Manhattan and had a significant effect on global markets, closing Wall Street until September 17 and the civilian airspace in the U.S. and Canada until September 13. Many closings, evacuations, and cancellations followed, out of respect or fear of further attacks. Cleanup of the World Trade Center site was completed in May 2002, and the Pentagon was repaired within a year. On November 18, 2006, construction of One World Trade Center began at the World Trade Center site. The building was officially opened on November 3, 2014. Numerous memorials have been constructed, including the National September 11 Memorial & Museum in New York City, the Pentagon Memorial in Arlington County, Virginia, and the Flight 93 National Memorial in a field in Stonycreek Township near Shanksville, Pennsylvania.

Planning of the attacks:

The idea for the attacks came from Khalid Sheikh Mohammed, who first presented it to Osama bin Laden in 1996. At that time, bin Laden and al-Qaeda were in a period of transition, having just relocated back to Afghanistan from Sudan. The 1998 African Embassy bombings and bin Laden’s 1998 fatwā marked a turning point, as bin Laden became intent on attacking the United States.

In late 1998 or early 1999, bin Laden gave approval for Mohammed to go forward with organizing the plot. A series of meetings occurred in early 1999, involving Mohammed, bin Laden, and his deputy Mohammed Atef. Atef provided operational support for the plot, including target selections and helping arrange travel for the hijackers. Bin Laden overruled Mohammed, rejecting some potential targets such as the U.S. Bank Tower in Los Angeles because, “there was not enough time to prepare for such an operation”.

Bin Laden provided leadership and financial support for the plot, and was involved in selecting participants. Bin Laden initially selected Nawaf al-Hazmi and Khalid al-Mihdhar, both experienced jihadists who had fought in Bosnia. Hazmi and Mihdhar arrived in the United States in mid-January 2000. In spring 2000, Hazmi and Mihdhar took flying lessons in San Diego, California, but both spoke little English, performed poorly with flying lessons, and eventually served as secondary – or “muscle” – hijackers.

In late 1999, a group of men from Hamburg, Germany arrived in Afghanistan, including Mohamed Atta, Marwan al-Shehhi, Ziad Jarrah, and Ramzi bin al-Shibh. Bin Laden selected these men because they were educated, could speak English, and had experience living in the West. New recruits were routinely screened for special skills and al-Qaeda leaders consequently discovered that Hani Hanjour already had a commercial pilot’s license. Mohammed later said that he helped the hijackers blend in by teaching them how to order food in restaurants and dress in Western clothing.

Hanjour arrived in San Diego on December 8, 2000, joining Hazmi. They soon left for Arizona, where Hanjour took refresher training. Marwan al-Shehhi arrived at the end of May 2000, while Atta arrived on June 3, 2000, and Jarrah arrived on June 27, 2000. Bin al-Shibh applied several times for a visa to the United States, but as a Yemeni, he was rejected out of concerns he would overstay his visa and remain as an illegal immigrant. Bin al-Shibh stayed in Hamburg, providing coordination between Atta and Mohammed. The three Hamburg cell members all took pilot training in South Florida.

In spring 2001, the secondary hijackers began arriving in the United States. In July 2001, Atta met with bin al-Shibh in Spain, where they coordinated details of the plot, including final target selection. Bin al-Shibh also passed along bin Laden’s wish for the attacks to be carried out as soon as possible. Some of the hijackers received passports from corrupt Saudi officials who were family members, or used fraudulent passports to gain entry.

Intelligence before the attacks:

In late 1999, al-Qaeda associate Khallad contacted Mihdhar, telling him to meet him in Kuala Lumpur, Malaysia; Hazmi and Abu Bara al Yemeni would also be in attendance. The NSA intercepted a telephone call mentioning the meeting, Mihdhar, and the name “Nawaf” (Hazmi). While the agency feared that “Something nefarious might be afoot”, it took no further action. The CIA had already been alerted by Saudi intelligence to the status of Mihdhar and Hazmi as al-Qaeda members, and a CIA team broke into Mihdhar’s Dubai hotel room and discovered that Mihdhar had a U.S. visa. While Alec Station alerted intelligence agencies worldwide about this fact, it did not share this information with the FBI. The Malaysian Special Branch observed the January 5, 2000, meeting of the two al-Qaeda members, and informed the CIA that Mihdhar, Hazmi, and Khallad were flying to Bangkok, but the CIA never notified other agencies of this, nor did it ask the State Department to put Mihdhar on its watchlist. An FBI liaison to Alec Station asked permission to inform the FBI of the meeting, but was told that “‘This is not a matter for the FBI.'”

By late June, senior counter-terrorism official Richard Clarke and CIA director George Tenet were “convinced that a major series of attacks was about to come”, although the CIA believed that the attacks would likely occur in Saudi Arabia or Israel. In early July, Clarke put domestic agencies on “full alert”, telling them that “Something really spectacular is going to happen here… soon.” He asked the FBI and the State Department to alert the embassies and police departments, and the Defense Department to go to “Threat Condition Delta.” Clarke would later write that “Somewhere in CIA there was information that two known al Qaeda terrorists had come into the United States… in [the] FBI there was information that strange things had been going on at flight schools in the United States… They had specific information about individual terrorists… None of that information got to me or the White House.”

On July 13, Tom Wilshire, a CIA agent assigned to the FBI’s international terrorism division, emailed his superiors at the CIA’s Counterterrorism Center (CTC), requesting permission to inform the FBI that Hazmi was in the country and that Mihdhar had a U.S. visa. However, the CIA never responded.

The same day in July, Margarette Gillespie, an FBI analyst working in the CTC, was told to review material about the Malaysia meeting. She was not told of the participants’ presence in the U.S. However, the CIA did give Gillespie surveillance photos of Mihdhar and Hazmi from the meeting to show to FBI counterterrorism, but did not tell her their significance. The Intelink database informed her not to share intelligence material on the meeting to criminal investigators. When shown the photos, the FBI were refused more details on their significance, and also did not receive Mihdhar’s date of birth or passport number. In late August 2001, Gillespie told the INS, the State Department, the Customs Service, and the FBI to put Hazmi and Mihdhar on their watchlists, but the FBI was prohibited from using criminal agents in the search for the duo, which hindered their efforts.

Also in July, a Phoenix-based FBI agent sent a message to FBI headquarters, Alec Station, and to FBI agents in New York, alerting them to “the possibility of a coordinated effort by Osama bin Laden to send students to the United States to attend civil aviation universities and colleges.” The agent, Kenneth Williams, suggested the need to interview all flight school managers and identify all Arab students seeking flight training. In July, Jordan alerted the U.S. that al-Qaeda was planning an attack on the U.S.; “months later”, Jordan notified the U.S. that the attack’s codename was “The Big Wedding”, and that it involved airplanes.

On August 6, the CIA’s Presidential Daily Brief, designated “For the President Only”, was entitled “Bin Ladin Determined to Strike in U.S.” The memo noted that “The FBI information… indicates patterns of suspicious activity in this country consistent with preparations for hijackings or other types of attacks.”

In mid-August, one Minnesota flight school alerted the FBI to Zacarias Moussaoui, who had asked “suspicious questions.” The FBI found that he was a radical who had traveled to Pakistan, and the INS arrested him for overstaying his French visa. However, their request to search his laptop was denied by FBI headquarters due to the lack of probable cause.

The failures in intelligence-sharing were attributed to 1995 Justice Department policies limiting intelligence sharing, combined with CIA and NSA reluctance in revealing “sensitive sources and methods” such as tapped phones. Testifying before the 9/11 Commission in April 2004, then-Attorney General John Ashcroft recalled that the “single greatest structural cause for the September 11th problem was the wall that segregated or separated criminal investigators and intelligence agents.” Clarke also wrote that “There were failures in the organizations… failures to get information to the right place at the right time…”

Attacks:

Flight paths of the four planes used on September 11.
Flight paths of the four planes used on September 11.

Early on the morning of September 11, 2001, 19 hijackers took control of four commercial airliners (two Boeing 757 and two Boeing 767) en route to California (three headed to LAX in Los Angeles, and one to SFO in San Francisco) after takeoffs from Logan International Airport in Boston, Massachusetts; Newark Liberty International Airport in Newark, New Jersey; and Washington Dulles International Airport in Loudoun and Fairfax counties in Virginia. Large planes with long flights were selected for hijacking because they would be heavily fueled.

The four flights were:

– American Airlines Flight 11: a Boeing 767 aircraft, departed Logan Airport at 7:59 a.m. en route to Los Angeles with a crew of 11 and 76 passengers, not including five hijackers. The hijackers flew the plane into the North Tower of the World Trade Center in New York City at 8:46 a.m.

– United Airlines Flight 175: a Boeing 767 aircraft, departed Logan Airport at 8:14 a.m. en route to Los Angeles with a crew of nine and 51 passengers, not including five hijackers. The hijackers flew the plane into the South Tower of the World Trade Center in New York City at 9:03 a.m.

– American Airlines Flight 77: a Boeing 757 aircraft, departed Washington Dulles International Airport at 8:20 a.m. en route to Los Angeles with a crew of six and 53 passengers, not including five hijackers. The hijackers flew the plane into the Pentagon in Arlington County, Virginia, at 9:37 a.m.

– United Airlines Flight 93: a Boeing 757 aircraft, departed Newark International Airport at 8:42 a.m. en route to San Francisco, with a crew of seven and 33 passengers, not including four hijackers. As passengers attempted to subdue the hijackers, the aircraft crashed into a field in Stonycreek Township near Shanksville, Pennsylvania, at 10:03 a.m.

Media coverage was extensive during the attacks and aftermath, beginning moments after the first crash into the World Trade Center.

Events:

Diagram showing the attacks on the World Trade Center.
Diagram showing the attacks on the World Trade Center.

At 8:46 a.m., five hijackers crashed American Airlines Flight 11 into the northern façade of the World Trade Center’s North Tower (1 WTC), and at 9:03 a.m., another five hijackers crashed United Airlines Flight 175 into the southern façade of the South Tower (2 WTC). Five hijackers flew American Airlines Flight 77 into the Pentagon at 9:37 a.m. A fourth flight, United Airlines Flight 93, under the control of four hijackers, crashed near Shanksville, Pennsylvania, southeast of Pittsburgh, at 10:03 a.m. after the passengers fought the hijackers. Flight 93’s target is believed to have been either the Capitol or the White House. Flight 93’s cockpit voice recorder revealed crew and passengers tried to seize control of the plane from the hijackers after learning through phone calls that Flights 11, 77, and 175 had been crashed into buildings that morning. Once it became evident to the hijackers that the passengers might regain control of the plane, the hijackers rolled the plane and intentionally crashed it.

Some passengers and crew members who called from the aircraft using the cabin airphone service and mobile phones provided details: several hijackers were aboard each plane; they used mace, tear gas, or pepper spray to overcome attendants; and some people aboard had been stabbed. Reports indicated hijackers stabbed and killed pilots, flight attendants, and one or more passengers. According to the 9/11 Commission’s final report, the hijackers had recently purchased multi-function hand tools and assorted Leatherman-type utility knives with locking blades, which were not forbidden to passengers at the time, but were not found among the possessions left behind by the hijackers. A flight attendant on Flight 11, a passenger on Flight 175, and passengers on Flight 93 said the hijackers had bombs, but one of the passengers said he thought the bombs were fake. The FBI found no traces of explosives at the crash sites, and the 9/11 Commission concluded that the bombs were probably fake.

Three buildings in the World Trade Center collapsed due to fire-induced structural failure. The South Tower collapsed at 9:59 a.m. after burning for 56 minutes in a fire caused by the impact of United Airlines Flight 175 and the explosion of its fuel. The North Tower collapsed at 10:28 a.m. after burning for 102 minutes. When the North Tower collapsed, debris fell on the nearby 7 World Trade Center building (7 WTC), damaging it and starting fires. These fires burned for hours, compromising the building’s structural integrity, and 7 WTC collapsed at 5:21 p.m. The west side of the Pentagon sustained significant damage.

At 9:42 a.m., the Federal Aviation Administration (FAA) grounded all civilian aircraft within the continental U.S., and civilian aircraft already in flight were told to land immediately. All international civilian aircraft were either turned back or redirected to airports in Canada or Mexico, and were banned from landing on United States territory for three days. The attacks created widespread confusion among news organizations and air traffic controllers. Among the unconfirmed and often contradictory news reports aired throughout the day, one of the most prevalent said a car bomb had been detonated at the U.S. State Department’s headquarters in Washington, D.C. Another jet—Delta Air Lines Flight 1989—was suspected of having been hijacked, but the aircraft responded to controllers and landed safely in Cleveland, Ohio.

In an April 2002 interview, Khalid Sheikh Mohammed and Ramzi bin al-Shibh, who are believed to have organized the attacks, said Flight 93’s intended target was the United States Capitol, not the White House. During the planning stage of the attacks, Mohamed Atta, the hijacker and pilot of Flight 11, thought the White House might be too tough a target and sought an assessment from Hani Hanjour (who hijacked and piloted Flight 77). Mohammed said al-Qaeda initially planned to target nuclear installations rather than the World Trade Center and the Pentagon, but decided against it, fearing things could “get out of control”. Final decisions on targets, according to Mohammed, were left in the hands of the pilots.

Casualties:

The remains of 6, 7, and 1 WTC on September 17, 2001.
The remains of 6, 7, and 1 WTC on September 17, 2001.

The attacks resulted in the deaths of 2,996 people and the injuries of more than 6,000 others. The death toll included 265 on the four planes (from which there were no survivors), 2,606 in the World Trade Center and in the surrounding area, and 125 at the Pentagon. Nearly all of those who perished were civilians with the exceptions of 343 firefighters, 72 law enforcement officers, 55 military personnel, and the 19 terrorists who died in the attacks. After New York, New Jersey lost the most state citizens, with the city of Hoboken having the most citizens that died in the attacks. More than 90 countries lost citizens in the September 11 attacks. The attacks of September 11, 2001, marked it the worst terrorist attack in world history and the deadliest foreign attack on American soil since the attack on Pearl Harbor on December 7, 1941.

In Arlington County, Virginia, 125 Pentagon workers lost their lives when Flight 77 crashed into the western side of the building. Of these, 70 were civilians and 55 were military personnel, many of them who worked for the United States Army or the United States Navy. The Army lost 47 civilian employees, six civilian contractors, and 22 soldiers, while the Navy lost six civilian employees, three civilian contractors, and 33 sailors. Seven Defense Intelligence Agency (DIA) civilian employees were also among the dead in the attack, as well as an Office of the Secretary of Defense (OSD) contractor. Lieutenant General Timothy Maude, an Army Deputy Chief of Staff, was the highest-ranking military official killed at the Pentagon.

In New York City, more than 90% of the workers and visitors who died in the towers had been at or above the points of impact. In the North Tower, 1,355 people at or above the point of impact were trapped and died of smoke inhalation, fell or jumped from the tower to escape the smoke and flames, or were killed in the building’s eventual collapse. The destruction of all three staircases in the tower when Flight 11 hit made it impossible for anyone above the impact zone to escape. 107 people below the point of impact died as well.

In the South Tower, one stairwell, Stairwell A, was left intact after Flight 175 hit, allowing 14 people located on the floors of impact (including one man who saw the plane coming at him) and four more from the floors above to escape. New York City 911 operators who received calls from individuals inside the tower were not well informed of the situation as it rapidly unfolded and as a result, told callers not to descend the tower on their own. In total 630 people died in that tower, fewer than half the number killed in the North Tower. Casualties in the South Tower were significantly reduced by some occupants deciding to start evacuating as soon as the North Tower was struck.

Urban Search and Rescue Task Force German Shepherd dog works to uncover survivors at the site of the collapsed World Trade Center after the September 11, 2001, attacks.
Urban Search and Rescue Task Force German Shepherd dog works to uncover survivors at the site of the collapsed World Trade Center after the September 11, 2001, attacks.

At least 200 people fell or jumped to their deaths from the burning towers, landing on the streets and rooftops of adjacent buildings hundreds of feet below. Some occupants of each tower above the point of impact made their way toward the roof in hope of helicopter rescue, but the roof access doors were locked. No plan existed for helicopter rescues, and the combination of roof equipment and thick smoke and intense heat prevented helicopters from approaching. A total of 411 emergency workers died as they tried to rescue people and fight fires. The New York City Fire Department (FDNY) lost 343 firefighters, including a chaplain and two paramedics. The New York City Police Department (NYPD) lost 23 officers. The Port Authority Police Department (PAPD) lost 37 officers. Eight emergency medical technicians (EMTs) and paramedics from private emergency medical services units were killed.

Cantor Fitzgerald L.P., an investment bank on the 101st–105th floors of the North Tower, lost 658 employees, considerably more than any other employer. Marsh Inc., located immediately below Cantor Fitzgerald on floors 93–100, lost 358 employees, and 175 employees of Aon Corporation were also killed. The National Institute of Standards and Technology (NIST) estimated that about 17,400 civilians were in the World Trade Center complex at the time of the attacks. Turnstile counts from the Port Authority suggest 14,154 people were typically in the Twin Towers by 8:45 a.m. Most people below the impact zone safely evacuated the buildings.

Weeks after the attack, the death toll was estimated to be over 6,000, more than twice the number of deaths eventually confirmed. The city was only able to identify remains for about 1,600 of the World Trade Center victims. The medical examiner’s office collected “about 10,000 unidentified bone and tissue fragments that cannot be matched to the list of the dead”. Bone fragments were still being found in 2006 by workers who were preparing to demolish the damaged Deutsche Bank Building. In 2010, a team of anthropologists and archaeologists searched for human remains and personal items at the Fresh Kills Landfill, where seventy-two more human remains were recovered, bringing the total found to 1,845. DNA profiling continues in an attempt to identify additional victims. The remains are being held in storage in Memorial Park, outside the New York City Medical Examiner’s facilities. It was expected that the remains would be moved in 2013 to a repository behind a wall at the 9/11 museum. In July 2011, a team of scientists at the Office of Chief Medical Examiner was still trying to identify remains, in the hope that improved technology will allow them to identify other victims. On March 20, 2015, the 1,640th victim was identified. There are still 1,113 victims who have not been identified.

Damage:

World Trade Center site (Ground Zero) with an overlay showing the original building locations.
World Trade Center site (Ground Zero) with an overlay showing the original building locations.

Along with the 110-floor Twin Towers, numerous other buildings at the World Trade Center site were destroyed or badly damaged, including WTC buildings 3 through 7 and St. Nicholas Greek Orthodox Church. The North Tower, South Tower, the Marriott Hotel (3 WTC), and 7 WTC were completely destroyed. The U.S. Customs House (6 World Trade Center), 4 World Trade Center, 5 World Trade Center, and both pedestrian bridges connecting buildings were severely damaged. The Deutsche Bank Building on 130 Liberty Street was partially damaged and demolished some years later, starting in 2007. The two buildings of the World Financial Center also suffered damage.

The Pentagon was damaged by fire and partly collapsed.
The Pentagon was damaged by fire and partly collapsed.

The Deutsche Bank Building across Liberty Street from the World Trade Center complex was later condemned as uninhabitable because of toxic conditions inside the office tower, and was deconstructed. The Borough of Manhattan Community College’s Fiterman Hall at 30 West Broadway was condemned due to extensive damage in the attacks, and is being rebuilt. Other neighboring buildings (including 90 West Street and the Verizon Building) suffered major damage but have been restored. World Financial Center buildings, One Liberty Plaza, the Millenium Hilton, and 90 Church Street had moderate damage and have since been restored. Communications equipment on top of the North Tower was also destroyed, but media stations were quickly able to reroute the signals and resume their broadcasts.

The Pentagon was severely damaged by the impact of American Airlines Flight 77 and ensuing fires, causing one section of the building to collapse. As the airplane approached the Pentagon, its wings knocked down light poles and its right engine hit a power generator before crashing into the western side of the building. The plane hit the Pentagon at the first-floor level. The front part of the fuselage disintegrated on impact, while the mid and tail sections kept moving for another fraction of a second. Debris from the tail section penetrated furthest into the building, breaking through 310 feet (94 m) of the three outermost of the building’s five rings.

Rescue efforts:

An injured victim of the Pentagon attack is evacuated.
An injured victim of the Pentagon attack is evacuated.

The New York City Fire Department deployed 200 units (half of the department) to the World Trade Center. Their efforts were supplemented by numerous off-duty firefighters and emergency medical technicians. The New York City Police Department sent Emergency Service Units and other police personnel, and deployed its aviation unit. Once on the scene, the FDNY, the NYPD, and the PAPD did not coordinate efforts and performed redundant searches for civilians. As conditions deteriorated, the NYPD aviation unit relayed information to police commanders, who issued orders for its personnel to evacuate the towers; most NYPD officers were able to safely evacuate before the buildings collapsed. With separate command posts set up and incompatible radio communications between the agencies, warnings were not passed along to FDNY commanders.

After the first tower collapsed, FDNY commanders issued evacuation warnings; however, due to technical difficulties with malfunctioning radio repeater systems, many firefighters never heard the evacuation orders. 9-1-1 dispatchers also received information from callers that was not passed along to commanders on the scene. Within hours of the attack, a substantial search and rescue operation was launched. After months of around-the-clock operations, the World Trade Center site was cleared by the end of May 2002.

September 11th Terrorist Attacks

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