The September 11 commission and its findings

In 2002 President Bush had appointed a commission to look into the September 11 attacks, and two years later it issued its final report. The commission found that the key pre-September 11 failure at the CIA was its not adding to the State Department’s “watch list” two of the “muscle” hijackers (who were trained to restrain the passengers on the plane), the suspected al-Qaeda militants Nawaf al-Hazmi and Khalid al-Mihdhar. The CIA had been tracking Hazmi and Mihdhar since they attended a terrorist summit meeting in Kuala Lumpur, Malaysia, on January 5, 2000. The failure to watch-list the two al-Qaeda suspects with the Department of State meant that they entered the United States under their real names with ease. On January 15, 2000, 10 days after the Malaysian meeting, Hazmi and Mihdhar flew into Los Angeles. The CIA also did not alert the FBI about the identities of the suspected terrorists, which could have helped the bureau locate them once they were inside the United States. According to the commission, this was the failure of not just a few employees at the CIA but a large number of CIA officers and analysts. Some 50 to 60 CIA employees read cables about the two al-Qaeda suspects without taking any action. Some of those officers knew that one of the al-Qaeda suspects had a visa for the United States, and by May 2001 some knew that the other suspect had flown to Los Angeles.

The soon-to-be hijackers would not have been difficult to find in California if their names had been known to law enforcement. Under their real names they rented an apartment, obtained driver’s licenses, opened bank accounts, purchased a car, and took flight lessons at a local school; Mihdhar even listed his name in the local phone directory.

It was only on August 24, 2001, as a result of questions raised by a CIA officer on assignment at the FBI, that the two al-Qaeda suspects were watch-listed and their names communicated to the FBI. Even then the FBI sent out only a “Routine” notice requesting an investigation of Mihdhar. A few weeks later Hazmi and Mihdhar were two of the hijackers on the American Airlines flight that plunged into the Pentagon.

The CIA inspector general concluded that "informing the FBI and good operational follow-through by CIA and FBI might have resulted in surveillance of both al-Mihdhar and al-Hazmi. Surveillance, in turn, would have had the potential to yield information on flight training, financing, and links to others who were complicit in the 9/11 attacks."

The key failure at the FBI was the handling of the Zacarias Moussaoui case. Moussaoui, a French citizen of Moroccan descent, was attending flight school in the summer of 2001 in Minnesota, where he attracted attention from instructors because he had little knowledge of flying and did not behave like a typical aviation student. The flight school contacted the FBI, and on August 16 Moussaoui was arrested on a visa overstay charge. Although Moussaoui was not the "20th hijacker," as was widely reported later, he had received money from one of the September 11 coordinators, Ramzi Binalshibh, and by his own account was going to take part in a second wave of al-Qaeda attacks following the assaults on New York and Washington.

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The FBI agent in Minneapolis who handled Moussaoui’s case believed that he might have been planning to hijack a plane, and the agent was also concerned that Moussaoui had traveled to Pakistan, which was a red flag as militants often used the country as a transit point to travel to terrorist training camps in Afghanistan. On August 23 (or 24, according to some reports) CIA director George Tenet was told about the case in a briefing titled "Islamic Extremist Learns to Fly." But FBI headquarters determined that there was not sufficient "probable cause" of a crime for the Minneapolis office to conduct a search of Moussaoui’s computer hard drive and belongings. Such a search would have turned up his connection to Binalshibh, according to Republican Sen. Charles Grassley, a leading member of the Senate Judiciary Committee, which has oversight of the FBI. The 9-11 Commission also concluded that “a maximum U.S. effort to investigate Moussaoui conceivably could have unearthed his connection to Binalshibh.”

The hunt for bin Laden

In September 2001 President Bush announced that he wanted Osama bin Laden captured—dead or alive—and a $25 million bounty was eventually issued for information leading to the killing or capture of bin Laden. Bin Laden evaded capture, however, including in December 2001, when he was tracked by U.S. forces to the mountains of Tora Bora in eastern Afghanistan. Bin Laden’s trail subsequently went cold, and he was thought to be living somewhere in the Afghanistan-Pakistan tribal regions.

U.S. intelligence eventually located him in Pakistan, living in the garrison city of Abbottabad, and in the early morning hours of May 2, 2011, on orders from U.S. Pres. Barack Obama, a small team of U.S. Navy SEALs assaulted his compound and shot and killed the al-Qaeda leader.

Health issues associated with the September 11 attacks

As a result of the destruction of the Twin Towers, one of the most densely populated areas on the planet was bathed in a coating of ash, pulverized rubble, and toxic particulates. Fires at Ground Zero and the collapsed 7 World Trade Center continued to smoulder and flare into 2002, exposing first responders to a witches’ brew of carcinogenic smoke. In the immediate aftermath of the attacks, firefighters and rescue and recovery workers began to report a range of health issues, particularly respiratory problems. Most common was a collection of ailments that came to be called “WTC Cough Syndrome”—a chronic sinus infection paired with symptoms that resembled asthma or bronchitis and often complicated by gastroesophageal reflux disease.

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As hours and days turned into weeks and months, people who lived, worked, or attended school in Lower Manhattan and Brooklyn began to report an assortment of physical and mental health concerns. It was estimated that some 400,000 people were “exposed to toxic contaminants, risk of physical injury, and physically and emotionally stressful conditions” as a result of the September 11 attacks. Many of those experiencing these issues struggled to gain recognition of their situation; police and firefighters often had their disability claims denied, despite experiencing debilitating respiratory illness. In 2010 Pres. Barack Obama signed the James Zadroga 9/11 Health and Compensation Act, a bill that was authored to address these shortfalls. The bill was named for James Zadroga, a New York City police detective who spent over 450 hours at Ground Zero; he contracted black lung and died in 2006 at the age of 34. The Zadroga Act created the World Trade Center Health Program, a Centers for Disease Control and Prevention initiative that treated and monitored survivors of the attack. By 2023 more than 5,700 participants in the program had died; it was estimated that deaths caused by September 11-related illnesses had far eclipsed the nearly 3,000 who had been killed in the attacks themselves.

One World Trade Center and the National September 11 Memorial and Museum

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The physical and symbolic void left by the destruction of the Twin Towers was filled on November 3, 2014, with the opening of One World Trade Center, a 1,776-foot (541.3-metre) skyscraper, which instantly became a dramatic new landmark on the Manhattan skyline. Adjacent to One World Trade Center are the National September 11 Memorial and Museum (completed in 2011 and 2014, respectively). Within the 8-acre (3.2-hectare) memorial plaza, twin 1-acre (0.4-hectare) reflecting pools occupy the footprints of the Twin Towers. The pools feature the largest man-made waterfalls in North America and are edged by bronze panels inscribed with the names of the victims of the September 11 attacks as well as the names of the six people who died as a result of the truck bombing of the World Trade Center in February 1993. Among more than 400 trees in the grove that surrounds the pools is the “Survivor Tree,” a Callery pear tree that was discovered badly damaged at Ground Zero, removed and nursed back to health, and then returned to the site in 2010. The memorial and plaza were designed by architects Michael Arad and Peter Walker, winners of a design competition that featured 5,201 submissions from 63 countries.

The museum includes a glass-encased pavilion with an atrium that features two 80-foot (24-metre) trident-shaped steel columns that were part of the facade of the North Tower. The museum’s Memorial Hall is adorned with 2,983 tiles (representing the victims of the September 2001 and February 1993 attacks), each one a blue watercolour with which artist Spencer Finch attempted to capture the colour of the sky on the day of the September 11 attacks. At the centre of the tiles is a quote from Virgil’s Aeneid:

No day shall erase you from the memory of time

The museum’s Foundation Hall is a high-ceilinged, nearly 15,000-square-foot (1,400-square-metre) room that encompasses part of a surviving retaining wall of the World Trade Center and displays the “Last Column,” a 36-foot (11-metre) steel beam to which workers and others attached messages and posters during Ground Zero cleanup operations. The international impact of the September 11 attacks is demonstrated along the ramp that descends into the museum by a multimedia exhibit featuring recorded reminiscences by people from 43 countries in 28 languages.