In the United States on September 11, 2001 (9/11), 19 terrorists from al-Qaeda hijacked four airplanes in an attempt to crash them into landmarks that symbolized American political and economic power. American Airlines Flight 11 and United Airlines Flight 175 crashed into the World Trade Center, and American Airlines Flight 77 was crashed into the Pentagon. United Airlines Flight 93 was intended to be crashed likely into the U.S. Capitol or White House, but the hijackers intentionally crashed it into a field in Pennsylvania instead, due to a passenger revolt.
Initially, al-Qaeda official Khalid Sheikh Mohammed planned to bomb multiple airliners departing Asia for the U.S. in 1995; the plot was foiled by Manila police before it was enacted. In 1996, he redesigned the plan, wanting nine U.S. airliners to be crashed into U.S. landmarks; al-Qaeda's leader, Osama bin Laden, rejected the plan over its complexity. In 1999, the pair and Mohammed Atef reworked it into what was ultimately carried out on 9/11.
Al-Qaeda then came into contact with the Hamburg cell, a terrorist cell in Germany led by Mohamed Atta. Some of the cell's members then visited camps in Afghanistan where al-Qaeda told them the plan, before the cell regrouped in Germany to work on it. Three of the members eventually piloted the hijacked planes on 9/11: Atta (Flight 11), Marwan al-Shehhi (175), and Ziad Jarrah (93). Flight 77's hijacker-pilot Hani Hanjour was not involved.
At least 19 men chosen by al-Qaeda entered the U.S. in 2000 and 2001. In addition, a potential 20th hijacker named Zacarias Moussaoui was arrested in Minnesota in August 2001. The 19 others split into four groups, and got tickets for four commercial flights on 9/11. During the hijackings, certain members of the groups attacked their respective flights' aircrews, likely using box cutters and mace, which let the others enter the planes' cockpits.
2,977 victims, plus all of the hijackers, died in the attacks. Many of the remaining conspirators in al-Qaeda were captured, then tortured during U.S. interrogations at CIA black sites or the Guantanamo Bay detention camp. Multiple federal investigations were made into 9/11, such as PENTTBOM and the 9/11 Commission. Investigators are split on if Saudi Arabia financed the attacks.
Background In the Soviet–Afghan War (1979–1989), Muslim-majority Afghanistan was invaded by the mostly non-Muslim Soviet Union. Osama bin Laden, a Saudi Islamist connected to the royal House of Saud, left his country to organize the Afghan mujahideen, Muslims who fought the Soviets as jihadists; those who engage in jihad, Islamic religious struggle, are called mujahideen. For that purpose, bin Laden and Abdullah Yusuf Azzam founded Maktab al-Khidamat (MaK). After the Soviets withdrew from Afghanistan in 1989, Azzam was assassinated in Pakistan. Bin Laden then took full control of MaK, which was absorbed into his organization al-Qaeda.
Due to bin Laden's beliefs, in 1991, the royals exiled him from Saudi Arabia. He moved to Sudan, where he may have had al-Qaeda get involved in the 1993 assault on U.S. troops in Somalia. In 1996, under Saudi and American pressure, Sudan exiled him from their country. Bin Laden returned to Afghanistan, which, by then, was run by the Taliban. They allowed al-Qaeda to use the country as its base of operations.
In 1996, bin Laden issued a fatwa calling for the American troops stationed in Saudi Arabia to leave. He issued another in 1998, calling for all Muslims to take up arms against Americans. He stated that, in choosing targets of their terrorist acts, the organization would not differentiate between civilians and soldiers: "As far as we are concerned, Americans are all targets."
In August 1998, al-Qaeda bombed two U.S. embassies in Kenya and Tanzania.Plotz, David (2001) What Does Osama Bin Laden Want? , Slate In 1999, the organization failed in an attempt to bomb Los Angeles International Airport (LAX) on New Year's Eve—one of many attacks they had planned to around the start of the new millennium. Shortly before New Year's, the planned perpetrator, Ahmed Ressam, tried to drive into the U.S. at the Canadian border, but border guards caught him with bomb-making material in his car. al-Qaeda also failed in an attempt to bomb USS The Sullivans, a U.S. Navy ship, on January 3, 2000. In October, they successfully bombed USS Cole while she docked in Yemen, by sailing a small radio-controlled boat up to her, then detonating a remote-controlled bomb that was on the boat. U.S. investigators suspected that "Islamic militants led [by] Osama bin Laden" were the perpetrators.
1990s–1996: Origins of the hijacking plan In the early 1990s, a Pakistani veteran of the Afghan mujahideen, Khalid Sheikh Mohammed, rose through the ranks of al-Qaeda to become a top lieutenant of bin Laden. During that time, he devised a plan for a series of terrorist attacks by al-Qaeda targeting airliners, which he codenamed "Bojinka"—allegedly a "nonsense word" he once heard in Afghanistan. In the "Bojinka plot", al-Qaeda and another group, Jemaah Islamiyah, planned for eleven planes departing Southeast Asia towards the United States to simultaneously be destroyed over the Pacific, via liquid bombs made by mixing chemicals.
In 1993, a group of al-Qaeda members that included Mohammed's nephew, Ramzi Yousef, bombed the underground portion of the World Trade Center (WTC) business complex in New York City, killing six people and injuring more than a thousand. Afterwards, in his apartment in Manila, Yousef and other conspirators started mixing chemicals to make the bombs for the Bojinka attacks. In 1994, Yousef rehearsed the bombings twice. One was set off at a Manila theater, the other inside Philippines Airlines Flight 434 mid-flight, killing one passenger.
In 1995, weeks before the planned bombings, the plot was foiled when Yousef's apartment burned down; investigating the fire, police found his laptop, which contained a file named "Bojinka", as well as a number of items that he fitted to carry out the bombing, but theoretically look inconspicuous to airport security. These included dolls fitted with clothes that contained nitrocellulose, a highly flammable compound. Yousef was captured by Pakistan in February 1995, and turned over to the U.S., where he was sentenced to life in prison. Investigators publicized the plan for the Bojinka plot. The Los Angeles Times reported in May that Western and Philippine officials were concerned about former Afghan mujahideen fighters who planned to commit terrorist acts in the name of Islam. Mohammed continued working on his idea regarding hijacked airliners.
1996–1999: Plan redesigns In 1996, Mohammed presented a modified version of the Bojinka plot idea to bin Laden in Afghanistan.Suspect 'reveals 9/11 planning' , BBC News Al-Qaeda members would hijack ten airplanes departing from across the U.S., and nine would be crashed into the World Trade Center; the U.S. Capitol and the FBI's headquarters, in Washington, D.C.; the Pentagon in Arlington County, Virginia; the CIA's headquarters in Langley, Virginia; the Columbia Center in Seattle; the Library Tower (now the U.S. Bank Tower) in Los Angeles; and an undetermined nuclear power plant. At the time, the Columbia Center and the Library Tower were the tallest skyscrapers in Washington state and California, respectively.
Mohammed himself would be a hijacker on the tenth plane, which would not crash; instead, he would help killing every adult male passenger onboard, and land in an undetermined U.S. airport. There, he would give a speech to the public denouncing U.S. policy towards Israel, the Philippines, and the Arab nations, and after he was finished, the women and children would be released unharmed. Nothing came of the plan at the time, as bin Laden rejected it for being too elaborate.9/11 Commission Report, Chapter 5 Mohammed later recalled that, "as we studied various targets, nuclear facilities arose as a key option", but they were discarded after concerns that the plan would "get out of hand".
In late 1998 or early 1999, bin Laden summoned Mohammed to Kandahar, Afghanistan, and approved for him to proceed with a scaled back version of the plan. Ayman al-Zawahiri, who had become bin Laden's deputy in 1998, convinced bin Laden to go through with the attacks, and built the "systematic organisation" that allowed al-Qaeda to enact them. In the spring of 1999, bin Laden, Mohammed, and bin Laden's deputy, Mohammed Atef, held a series of meetings where they designed the final version of the general plan, which was ultimately carried out on 9/11. They came up with a rule the hijacker-pilots of the planes would follow: that if they could not reach their intended target, they were to crash the plane at its current location. They listed potential targets that each symbolized to them the U.S.'s global power, including the World Trade Center, representing America's economy; the Pentagon, its military; the U.S. Capitol, its support of Israel; and the White House in D.C., its politics.
1990s–2000: Hamburg cell
In 1992, an Egyptian architect named Mohamed Atta moved to Germany to study urban planning at university in Hamburg. Four years later, he began attending the local al-Quds Mosque, popular with Islamist men. Atta was radicalized towards Islamism, either by meeting those men, or being directly contacted by an agent of bin Laden. He then became the ringleader of the Hamburg cell, a clandestine cell system of Islamic extremist terrorists who lived in the city prior to 9/11. The cell were likely planning their own jihadist activities in Russia when they met al-Qaeda's leadership, and then joined the organization in late 1999 to work on the details of al-Qaeda's redesigned hijacking plan.
Besides Atta, eleven men were members: Abdelghani Mzoudi, Ahmed Taleb, Mamoun Darkazanli, Marwan al-Shehhi, Mohammed Haydar Zammar, Mounir el-Motassadeq, Naamen Meziche, Ramzi bin al-Shibh, Said Bahaji, Zakariya Essabar, and Ziad Jarrah. Atta, al-Shehhi, and Jarrah were hijacker-pilots on 9/11. Like Atta, many of the members came to Hamburg for education, and were radicalized at the al-Quds Mosque—which was run by Darkazanli. Zammar had been in the Muslim Brotherhood in Syria, as well as a jihadist fighter in the Bosnian War (1992–1995), and a war in Afghanistan. Different sources have described both Bahaji and Zammar as the single person who brought all the members together. Bahaji acted as the cell's computer expert, Essabar helped them tamper with and forge passports, and el-Motassadeq helped with logistics, paying some members' bills, such as the students' tuitions.
Over a few months in 1999, before most of them ever engaged in terrorist activities, the members watched footage of jihadists fighting in Chechnya, a region which is internationally recognized as a republic of Russia, but is populated by separatist Chechen groups, including Islamist militants. In the Second Chechen War (1999–2009), the Islamists waged defensive jihad against the Russian military. Watching the videos, the cell became motivated to join them in-person. In 2004, the U.S. government's 9/11 Commission claimed that the members boarded a train going east, the direction of Chechnya, in late 1999. By chance, an al-Qaeda member named "Khalid al-Masri" was onboard at the same time. He met the cell, and convinced them to join the organization. Before then, the commission found, the cell had no connection to al-Qaeda, and no intentions of attacking the U.S. The Commission's claim that "al-Masri" sent the cell to Duisburg, Germany, before they met al-Qaeda was later proven false.