What Were the 9/11 Attacks?
The September 11 attacks (widely written as 9/11) were four coordinated terrorist suicide attacks carried out by the militant group al-Qaeda against the United States on Tuesday, September 11, 2001. Nineteen hijackers seized control of four commercial passenger jets, using them as weapons.
Both Twin Towers collapsed within hours due to structural failure from the fires ignited by jet fuel.
| Flight | Time | Target / Location | Outcome |
|---|
| American Airlines Flight 11 | 8:46 AM | North Tower, World Trade Center, NYC | Crashed into the tower |
| United Airlines Flight 175 | 9:03 AM | South Tower, World Trade Center, NYC | Crashed into the tower |
| American Airlines Flight 77 | 9:38 AM | The Pentagon, Arlington, Virginia | Crashed into the west side |
| United Airlines Flight 93 | ~10:03 AM | Likely U.S. Capitol or White House | Passengers fought back; crashed near Shanksville, Pennsylvania |
Casualties
Nearly 3,000 people were killed, making 9/11 the deadliest terrorist attack in world history - World Trade Center: 2,753, Pentagon: 184, and Flight 93: 40.
Victims came from more than 90 countries. Hundreds of emergency workers — including 343 firefighters and 60 police officers — died while trying to rescue people.

Who Was Responsible?
The attacks were planned and organized by al-Qaeda, an Islamist extremist network led by Osama bin Laden, who was identified as the mastermind.
19 men, mostly from Saudi Arabia (with others from Egypt, the United Arab Emirates, and Lebanon), carried out the hijackings under bin Laden’s direction.
The U.S. officially identified al-Qaeda as responsible within days; bin Laden was killed in 2011.
Why The Attack
Al-Qaeda attacked because they opposed U.S. troops in Saudi Arabia, U.S. support for Israel, U.S. policies in Iraq and the Middle East, and U.S.-backed regional governments — all wrapped in an extremist religious ideology that declared it permissible to kill American civilians. These were their stated justifications, widely rejected as morally and religiously illegitimate.
U.S. military presence in Saudi Arabia
After the 1990 Iraqi invasion of Kuwait, U.S. forces were stationed in Saudi Arabia. Bin Laden considered the presence of non-Muslim American troops in what he regarded as sacred Islamic territory unacceptable.
U.S. support for Israel
Bin Laden strongly opposed U.S. support for Israel and viewed American policy toward the Israeli-Palestinian conflict as hostile to Muslims.
U.S. involvement in the Middle East
Al-Qaeda opposed American political and military influence in countries such as Iraq and Saudi Arabia.
U.S. sanctions against Iraq
Bin Laden also used American sanctions against Iraq during the 1990s as part of his argument that the United States was harming Muslims.
Why attack the World Trade Center?
The World Trade Center represented American economic power. The Pentagon represented American military power.
The fourth aircraft was apparently intended for another important U.S. government target, although its exact intended target remains uncertain. Passengers fought the hijackers, causing the plane to crash in Pennsylvania.
So the attacks were designed to strike highly symbolic American institutions.
After The Incident, Consequences & Impact
The attacks had major worldwide consequences, including the U.S.-led War on Terror, the invasion of Afghanistan, and significant changes to airport and national security.
The first major military response was the invasion of Afghanistan in October 2001, because the Taliban government was allowing al-Qaeda leader Osama bin Laden and his organization to operate from Afghanistan.
The Taliban was overthrown relatively quickly, but the resulting war lasted for nearly 20 years, until U.S. forces withdrew in 2021.
Broad U.S. economy: healed in ~3–4 months. New York City + aviation/tourism: took years. And the long-term costs (war, security, debt) lasted for decades — those were never "healed" in an economic sense.
The interesting thing is that the economy was already in a recession before 9/11. The dot-com bubble had burst in 2000, and the recession had officially begun in March 2001. So 9/11 deepened an existing economic downturn rather than creating a completely new recession.
New York City experienced substantial job and business losses, although the city's economy eventually recovered. Insurance faced enormous claims and losses.
Government spending increased dramatically because of military operations, homeland security, reconstruction, and other responses.
The destruction of the World Trade Center was enormous, but the WTC represented only a small fraction of the overall U.S. economy. The United States had an enormous and diversified economy, so destroying one major commercial complex could not by itself bring down the national economy.
15 of the 19 hijackers were Saudi citizens
All of the hijackers were members of al-Qaeda, and 15 of them were Saudi citizens.
The official 9/11 Commission investigated whether the Saudi government financed or supported the operation. It found no evidence that the Saudi government as an institution or senior Saudi officials individually funded al-Qaeda for the attacks - but some Saudi government-affiliated individuals did provide help to hijackers.
Some Saudi nationals with apparent connections to Saudi government institutions interacted with or assisted two hijackers after they arrived in California.
For example, Omar al-Bayoumi, a Saudi national who had connections to the Saudi government, helped hijackers Nawaf al-Hazmi and Khalid al-Mihdhar paid their rent, helped them get apartments and bank accounts. Years later, the FBI confirmed he was on the payroll of Saudi intelligence at the time. Phone records show dozens of calls from al-Bayoumi to Saudi consulate, embassy, and government offices while helping the hijackers.
And then there were the famous "28 pages"
In 2016, the U.S. released the previously classified 28-page section of a congressional investigation. It contained investigative leads concerning possible connections between Saudi government-linked individuals and people associated with the hijackers.
But this is important:
The 28 pages did not prove that the Saudi government ordered 9/11.
They documented suspicions, intelligence leads and connections that required investigation, rather than establishing that the Saudi government planned the attacks.
| Category | Status |
|---|
| Saudi government as a whole planned/directed it | ❌ NOT proven — no conclusive evidence |
| Senior Saudi officials officially involved | ❌ NOT proven |
| Individuals with Saudi government ties helped hijackers | ✅ Documented & confirmed |
| Saudi charities & private donors funding al-Qaeda | ✅ Confirmed — private Saudi money was al-Qaeda's main funding source |
The Saudi government as a whole was not proven to be involved in or to have ordered the 9/11 attacks. However, individuals connected to the Saudi government did provide logistical help to some hijackers. Whether those individuals were acting on official orders or on their own has never been definitively proven either way — and that is why the debate continues.
Who was Omar al-Bayoumi
Omar al-Bayoumi is a Saudi national who lived in San Diego, California. He claimed to be a graduate student/business student.
FBI later confirmed that he was on the payroll of Saudi intelligence (General Intelligence Presidency) and received regular funding from the Saudi Embassy in Washington.
What did he do?
In early 2000, two future 9/11 hijackers, Nawaf al-Hazmi and Khalid al-Mihdhar, arrived in California. Al-Bayoumi encountered them in a restaurant in the Los Angeles area.
He then encouraged them to move to San Diego, helped them find an apartment, co-signed their lease, helped them open a bank account, provided financial and practical assistance, and arranged for other people in the local Saudi/Muslim community to help them.
After meeting them, his allowance from Saudi sources increased significantly — a pattern that raised immediate suspicion.
Investigators found that he was receiving substantial financial support from a Saudi company connected to the Saudi Civil Aviation Authority. He also had extensive contacts with Saudi government institutions and people connected to the Saudi consulate.
Declassified FBI material later indicated that the FBI assessed al-Bayoumi as having worked as a Saudi intelligence asset/contact. However, exactly what his assignment was and whether his Saudi intelligence connections had anything to do with 9/11 remain disputed.
Most importantly, being connected to Saudi intelligence does not itself prove that he knew about or supported the 9/11 plot.
The original 9/11 Commission concluded that it had no credible evidence that al-Bayoumi believed in violent extremism or knowingly aided extremist groups.
Who was Fahad al-Thumairy
Fahad al-Thumairy was a Saudi religious official and diplomat in Los Angeles who became another important figure in investigations into possible Saudi connections to the 9/11 hijackers.
He had two roles at the same time, he was an accredited diplomat at the Saudi Consulate in Los Angeles (1996 until 2003) and also a Director of the King Fahd Mosque in Culver City, California. Officially an employee of the Saudi Ministry of Islamic Affairs — a government department.
When Nawaf al-Hazmi and Khalid al-Mihdhar, arrived in Los Angeles on January 15, 2000. According to later FBI material, the first place they visited was the King Fahd Mosque, where Thumairy was the imam.
Investigators became interested in Thumairy because they found evidence that he was connected to people who subsequently assisted the two hijackers. He knew al-Bayoumi well — they worked together at the mosque.
In particular, investigators suspected that Thumairy may have arranged for an associate to help Hazmi and Mihdhar with things such as transportation and lodging.
What Happened to Him
When interviewed by investigators, he was evasive, inconsistent, and refused to answer key questions.
Shortly after 9/11, the U.S. government revoked his diplomatic visa and expelled him from the country — meaning U.S. authorities considered him a security risk.
He returned to Saudi Arabia and was later promoted — became a senior official in the Ministry of Islamic Affairs. He was never charged, never extradited, never fully questioned.
No investigation has ever been able to prove whether they were acting on orders from Riyadh — or were sympathizers who abused their positions on their own. That is why the debate continues to this day.
Osama Bin Laden
There are two main questions, who were the people who helped the hijackers inside the United States, and who organized and commanded the 9/11 attack itself?
The evidence for the second question pointed toward al-Qaeda and Osama bin Laden very quickly, even while the first question remained full of unresolved Saudi connections.
Since bin Laden was already a known enemy of the United States before 9/11 - Bin Laden had declared war on the U.S. in 1996 and again in 1998, publicly stating it was his religious duty to kill Americans - the FBI placed bin Laden on its Ten Most Wanted list in 1999.
By 1998, al-Qaeda had carried out the bombings of the U.S. embassies in Kenya and Tanzania, killing more than 200 people. Then, in October 2000, al-Qaeda operatives attacked the USS Cole, killing 17 American sailors. So when four aircraft were hijacked in an operation that looked like a highly coordinated al-Qaeda-style attack, investigators weren't starting from zero.
Khalid Sheikh Mohammed (KSM)
The 9/11 Commission's investigation concluded that Khalid Sheikh Mohammed (KSM) was the principal architect of the operation.
KSM had approached bin Laden with the idea of using aircraft as weapons. By late 1998 or early 1999, bin Laden and his senior leadership had accepted the plan. Bin Laden then provided operatives for the operation and al-Qaeda began training people for it.
In November 2001, U.S. forces found a videotape in Afghanistan where bin Laden bragged about the attacks, discussing details only the mastermind could know. Later, he openly claimed responsibility.
Saudi Government
Bin Laden was definitely the mastermind. He planned it, paid for it, approved it, and admitted it. That part is proven.
But, that does not mean Saudi-affiliated people didn't assist him. The hijackers did receive help from people with Saudi government ties.
That help is documented. Whether that help was ordered from above or sympathizers acting alone was never fully investigated — because the U.S. government classified the evidence to protect the alliance.