The Ultimate 9/11 Quiz

2001 Islamist Terrorist Attacks in the United States

• The 9/11 attacks were four coordinated suicide terrorist attacks carried out by the militant Islamist extremist network al-Qaeda against the United States on September 11, 2001.

• Nineteen terrorists hijacked four commercial airliners scheduled to travel from the East Coast to California, and the hijackers crashed the first two planes into the Twin Towers of the World Trade Center in New York City, which were two of the top five tallest buildings in the world at the time.

• Following the first two impacts, the third and fourth flights were similarly coordinated to attack targets in the Washington metropolitan area. The third plane succeeded in crashing into the Pentagon, while the fourth was intended to strike a federal government building in D.C. itself but crashed in a Stonycreek, Pennsylvania field following a passenger revolt.

• The attacks killed nearly 3,000 people and instigated the global war on terror.

• Within hours of the attacks, the Central Intelligence Agency determined that al-Qaeda was responsible, and the United States formally responded by launching the war on terror and invading Afghanistan to depose the Taliban.

• The attacks resulted in 2,977 non-hijacker fatalities, an indeterminate number of injuries, and substantial long-term health consequences, in addition to at least $10 billion in infrastructure and property damage.

• It remains the deadliest terrorist attack in human history as well as the deadliest aviation-related disaster, and the single deadliest incident for firefighters and law enforcement officers in U.S. history.

• Bin Laden orchestrated the attacks and initially denied involvement, but later recanted his false statements.

• Khalid Sheikh Mohammed admitted his involvement in the attacks and was the principal architect of the 9/11 attacks.

• Bin Laden interpreted Muhammad as having banned the "permanent presence of infidels in Arabia", and in a December 1999 interview, bin Laden said he felt that Americans were "too near to Mecca", and considered this a provocation to the entire Muslim world.

• Some analysts, including political scientists John Mearsheimer and Stephen Walt, claimed that U.S. support of Israel was one motive for the attacks.

• Documents seized during the 2011 operation that killed bin Laden included a few notes handwritten by bin Laden in September 2002 with the heading "The Birth of the Idea of September 11", in which he describes how he was inspired by the crash of EgyptAir Flight 990 on October 31, 1999.Summary Title: The Planning and Execution of the 9/11 Attacks

• Khalid Sheikh Mohammed presented the idea of the 9/11 attacks to Osama bin Laden in 1996, and bin Laden gave approval for the plot in late 1998 or early 1999.

• Mohammed, bin Laden, and Mohammed Atef held a series of meetings in early 1999 to plan the attacks, with Atef providing operational support and bin Laden overruling Mohammed's target suggestions.

• Bin Laden selected the hijackers, including experienced jihadists Nawaf al-Hazmi and Khalid al-Mihdhar, who arrived in the US in mid-January 2000.

• In early 2000, Hazmi and Mihdhar took flying lessons in San Diego, but performed poorly and eventually served as secondary hijackers.

• Other hijackers, including Mohamed Atta, Marwan al-Shehhi, Ziad Jarrah, and Ramzi bin al-Shibh, arrived in the US in 2000 and took pilot training in South Florida.

• The attacks were planned for September 11, 2001, a date that bin Laden chose because it marked a time when the West gained dominance over Islam.

• The NSA intercepted a telephone call mentioning the Malaysia meeting between al-Qaeda members, but did not take further action.

• The CIA and FBI failed to share intelligence about the hijackers, despite warnings from Saudi intelligence and a Phoenix-based FBI agent's suggestion to interview all flight school managers and identify Arab students seeking flight training.

• The 9/11 attacks involved the hijacking of four commercial airliners en route to California, which were flown into the World Trade Center's North and South Towers, The Pentagon, and a field near Shanksville, Pennsylvania.

• The hijackers used boxcutters, bomb threats, and chemical weapons to take control of the planes and instill fear in passengers and crew members.

• Some passengers and crew members who called from the aircraft provided details of the hijackers' actions, including the use of mace and stabbings.

• The failures in intelligence-sharing were attributed to Justice Department policies limiting intelligence sharing and CIA and NSA reluctance to reveal sensitive sources and methods. Summary Title: Key Facts and Figures about the 9/11 Attacks

• The FBI found no traces of explosives at the crash sites, and the 9/11 Commission concluded that the bombs were probably fake.

• The South Tower collapsed first at 9:58 a.m. due to fire-induced structural failure, while the North Tower collapsed 29 minutes later at 10:28 a.m. after burning for 1 hour and 41 minutes.

• The attacks caused the deaths of 2,996 people (including the hijackers) and injured thousands of others, making it the deadliest act of terrorism in world history.

• Entirely because of the attacks on the World Trade Center, 2,606 people died, including 343 firefighters, 72 law enforcement officers, 55 military personnel, and the 19 terrorists.

• 125 Pentagon workers died when Flight 77 crashed into the building's western side, including 70 civilians and 55 military personnel.

• More than 200 people fell to their deaths from the burning towers, most of whom were forced to commit suicide by jumping to escape the extreme heat, fire, and smoke.

• A total of 414 emergency workers died as they tried to rescue people and fight fires, while another law enforcement officer was separately killed on-board United 93 as it crashed.

• 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 PATH train system's World Trade Center station was located under the complex and was demolished completely when the towers collapsed, but was rebuilt as the $4 billion World Trade Center Transportation Hub.

• The Pentagon was severely damaged by the impact of American Airlines Flight 77 and the ensuing fires, causing one section of the building to collapse.

• The New York City Fire Department deployed 200 units (half of the department) to the World Trade Center, while the NYPD sent Emergency Service Units and other police personnel and deployed its aviation unit.

• The rescue efforts were not well-coordinated between the FDNY, NYPD, and PAPD, with redundant searches for civilians being performed.

• The medical examiner's office collected "about 10,000 unidentified bone and tissue fragments that cannot be matched to the list of the dead," with 1,106 victims yet to be identified as of September 2021.Summary Title: Reactions to the 9/11 Attacks

• FDNY commanders issued evacuation warnings after the first tower collapsed, but technical difficulties with radio systems led to many firefighters not hearing the orders.

• The attacks resulted in immediate responses, including domestic and international reactions, military responses, and an extensive compensation program for victims and their families.

• FAA officials notified NORAD about Flight 11, which was hijacked, but due to communication issues, NORAD had only nine minutes' notice before the attack. Vice President Dick Cheney ordered the shooting down of hijacked planes, but the instructions were not relayed in time.

• Emergency preparedness plan SCATANA was invoked, stranding tens of thousands of passengers across the world. Congress was not told about the continuity of government status until February 2002.

• The Homeland Security Act of 2002 and the USA PATRIOT Act were enacted, but civil liberties groups criticized the latter for allowing law enforcement to invade citizens' privacy.

• Hate crimes and discrimination against Muslims and South Asians increased after the attacks, with many incidents reported across the country.

• Muslim organizations in the US swiftly condemned the attacks and provided assistance to victims and their families.

• International reactions were mainly supportive, with nations offering pro-American support and solidarity. Iraq was a notable exception, with the government's official statement condoning the attacks.

• Military operations were initiated, with the US and its allies invading Afghanistan to bring bin Laden and al-Qaeda to justice and prevent the emergence of other terrorist networks.

• The Authorization for Use of Military Force Against Terrorists was passed, granting the President the authority to use all "necessary and appropriate force" against those who planned, authorized, committed, or aided the 9/11 attacks or harbored said persons or groups.