9/11 Attack: Causes, Events, Survival and Aftermath Explained

For those who lived through September 11, 2001, the memory remains vivid: planes rerouted, phone lines overwhelmed, dust settling over lower Manhattan. Questions still surface decades later about the mechanics of the attacks, survival odds inside the towers, and what became of the nearly 3,000 who died.

Date: September 11, 2001 · Perpetrators: Al-Qaeda · Planes Hijacked: 4 · Targets Hit: World Trade Center, Pentagon

Key data points from official sources reveal the scale and progression of the attacks.

What caused 911 to happen?

Al-Qaeda, the extremist organization founded by Osama bin Laden, carried out the September 11 attacks as the climax of a years-long campaign of violence against American targets. The group issued statements declaring holy war against the United States, vowing death to Americans and demanding the withdrawal of U.S. military forces from the Middle East.

Al-Qaeda planning

Al-Qaeda operatives spent months training at flight schools in the United States while plotting the operation. The attackers obtained valid visas, blended into American communities, and practiced flying commercial jets without any intention of landing.

• Flight 11 departed Boston at 7:59 AM with 76 passengers, 11 crew, and 5 hijackers aboard (Miller Center)
• Flight 175 took off from Boston at 8:15 AM carrying 51 passengers, 9 crew, and 5 hijackers (Miller Center)

Hijacker motivations

The hijackers viewed the attacks as religious duty, interpreting their actions through a lens of Islamic jihad. The 9/11 Commission Report documented how the group justified mass civilian casualties as acceptable within their ideological framework.

What Were the 9/11 Terrorist Attacks?

On the morning of September 11, 2001, al-Qaeda terrorists hijacked four commercial passenger planes and turned them into weapons directed at the United States. The coordinated strikes killed nearly 3,000 people at three different sites.

Hijacked planes

• American Airlines Flight 11: Struck the North Tower between floors 93-99 at 8:46 AM (USA Today)
• United Airlines Flight 175: Hit the South Tower between floors 77-85 at 9:03 AM (USA Today)
• American Airlines Flight 77: Crashed into the Pentagon at 9:37 AM (Miller Center)
• United Airlines Flight 93: Crashed in Pennsylvania after passengers attempted to retake the plane at 10:03 AM (National Park Service)

Targets struck

The World Trade Center in lower Manhattan bore the heaviest toll, with both towers collapsing within two hours of the initial strike. The Pentagon attack killed 125 people on the ground. Flight 93 passengers thwarted a fourth attack, likely targeting the U.S. Capitol or White House.

Why did the Twin Towers fall if they were hit at the top?

The towers fell not because the upper floors collapsed under the planes’ weight, but because the impacts severed critical structural columns while simultaneously igniting fires that weakened the remaining steel framework. According to the 9/11 Commission Report, the combination of direct structural damage and fire-induced steel softening triggered progressive collapse.

Structural failure

The towers were engineered as steel tube structures with a perimeter of thin, closely spaced columns that provided much of the buildings’ strength. When jets struck, they sliced through multiple perimeter columns and core columns simultaneously, removing load-bearing capacity in seconds.

Fire and impact damage

• The jet fuel from both planes ignited fires that burned at temperatures sufficient to weaken structural steel
• Impact forces dislodged fireproofing from steel components, leaving them exposed to heat
• As damaged sections buckled under weight, undamaged sections could not support the redistributed loads
• The towers fell in a pattern resembling controlled demolition, with the upper portion pancaking onto lower floors

The 16-acre World Trade Center complex opened in 1973 and had previously survived the 1993 truck bombing that killed six people and injured over 1,000 (John Jay College Timeline). The February 26, 1993 bombing caused extensive damage to the parking garage beneath the towers, but structural engineers determined the buildings remained sound.

Did anyone on the top floors survive 9/11?

Survival above the impact zones was extraordinarily rare, but four people escaped from the South Tower by navigating an unblocked stairwell while everyone above the 81st floor perished in the North Tower.

Elevator miracle

In the South Tower, an estimated 16 minutes elapsed between the first and second plane crashes—enough time for some workers above the impact zone to attempt evacuation. Four people reached Stairway A, which remained passable below the impact zone. They descended through smoke and darkness to safety.

• The South Tower had four survivors above the impact zone (USA Today)
• No one survived above the 92nd floor in the North Tower (USA Today)
• Ron DiFrancesco, one of the four survivors, escaped from approximately the 91st floor of the South Tower

Stairway escape

The North Tower presented a grimmer picture. After Flight 11 struck between floors 93-99, all elevator shafts and stairwells were severed at the impact zone, trapping everyone on higher floors with no escape route. Employees on floors above the 91st floor faced certain death.

Many trapped in the South Tower went upward toward the roof, assuming helicopter rescue was possible. Roof access doors were locked, and smoke filled the upper floors, making that escape route impossible (USA Today).

Are there any people still missing from 9/11?

More than two decades after the attacks, the Office of the Chief Medical Examiner continues working to identify human remains recovered from the World Trade Center site. The work involves DNA analysis of fragments too small for earlier testing methods.

Victim identification

The process has grown more sophisticated over time. What initially seemed impossible to identify through visual recognition alone now yields results through genetic technology. Each match provides closure for families who have waited decades.

Ongoing lab work

According to the 9/11 Memorial, thousands of tissue fragments remain unmatched. The medical examiner periodically announces new identifications, sometimes decades after the initial recovery. Families receive confirmation when scientists link a fragment to their loved one’s DNA profile.

Notable near-misses

Several well-known individuals came close to being on the hijacked flights or were in the towers when the attacks occurred.

Mark Wahlberg was scheduled to fly on Flight 11 but changed his plans and missed the flight. He has spoken publicly about the experience.

— Multiple news reports on celebrity near-misses from 9/11

Everyone on floors 92 and up died; 99% of those below lived. The fate of nearly everyone inside the World Trade Center was sealed the moment the hijacked jets struck.

— USA Today detailed survivor analysis

The 16-minute interval between the two crashes created an unusual situation where some workers in the South Tower began evacuating from upper floors before the second impact. This partial evacuation window accounted for the four top-floor survivors in the South Tower versus zero in the North Tower.

Bottom line: Al-Qaeda killed nearly 3,000 people on September 11, but the numbers could have been far worse. Below the impact zones, 99% of workers survived—proof that early evacuation warnings save lives. The towers fell because fires weakened structural steel after impact damage, not because upper floors collapsed from plane weight alone. Four people above the South Tower impact zone escaped through an unblocked stairwell, while everyone above the North Tower impact zone died.