Tuesday, September 11, 2001, began with clear skies across much of the eastern United States. At 8:46 a.m., American Airlines Flight 11 struck the North Tower of the World Trade Center. Seventeen minutes later, United Airlines Flight 175 hit the South Tower in full view of television cameras. What had first appeared to be a catastrophic accident was now unmistakably a coordinated attack.
Four hijacked airliners, four crash sites and less than two hours transformed an ordinary morning into the deadliest terrorist attack in United States history. This account follows the documented sequence, the people caught within it, the institutional failures later investigated, and the long consequences that followed.
Four flights
Nineteen al-Qaeda operatives boarded four transcontinental flights departing from Boston, Washington Dulles and Newark. The aircraft were selected in part because they carried enough fuel for long journeys to the West Coast. The plot had developed over years under al-Qaeda leader Osama bin Laden, with Khalid Sheikh Mohammed serving as its principal operational architect.
American Airlines Flight 11 left Boston at 7:59 a.m. United Airlines Flight 175 departed from the same airport at 8:14. American Airlines Flight 77 took off from Washington Dulles at 8:20. United Airlines Flight 93 departed Newark at 8:42 after a delay. The hijackers seized the cockpits after takeoff, at a time when aviation security and response protocols were designed around older assumptions that a hijacked aircraft would land and become the subject of negotiation.
Flight attendants and passengers made calls from the aircraft. Their reports gave airlines and officials some of the first direct information about the hijackings. Air traffic controllers, the Federal Aviation Administration and the military were forced to interpret several rapidly changing crises without a shared picture of the entire plot.
New York: impact, evacuation and collapse
Flight 11 struck the North Tower between floors 93 and 99 at 8:46 a.m. Everyone aboard was killed. The impact destroyed all three stairways through the crash zone, trapping those above it. Thousands of people below began to evacuate while firefighters, police officers and emergency medical personnel moved toward the complex.
At 9:03 a.m., Flight 175 struck the South Tower between floors 77 and 85. The second impact confirmed the scale and intent of the attack. One stairwell remained passable, and a small number of people from above the impact zone used it to escape. Many others could not.
The South Tower collapsed at 9:59 after burning for 56 minutes. The North Tower collapsed at 10:28 after 102 minutes. The collapses killed civilians and hundreds of emergency responders. They also destroyed or severely damaged buildings across the World Trade Center site. At 5:20 p.m., 7 World Trade Center collapsed after hours of uncontrolled fires and damage; the building had been evacuated.
The National Institute of Standards and Technology later concluded that aircraft impacts damaged columns and dislodged fireproofing, while the resulting multi-floor fires weakened the structures. Its investigation led to recommendations and changes in building design, fire resistance, evacuation and emergency communications.
The Pentagon
At 9:37 a.m., Flight 77 struck the western side of the Pentagon in Arlington, Virginia. All 59 passengers and crew members aboard, excluding the five hijackers, were killed, along with 125 people inside the building.
The target carried an unusual historical echo. Construction of the Pentagon had begun on September 11, 1941, exactly sixty years earlier. In 2001, renovation work had strengthened part of the affected section, and emergency response continued amid fire, structural collapse and reports that other aircraft might still be approaching Washington.
Flight 93
Flight 93 was hijacked later than the other aircraft. Passengers and crew reached family members and airline personnel by telephone and learned that planes had struck the World Trade Center. They organized an attempt to regain control.
At 10:03 a.m., the hijackers crashed the aircraft into a field near Shanksville, Pennsylvania, as passengers and crew fought back. All 40 passengers and crew members, excluding the four hijackers, were killed. The 9/11 Commission concluded that the hijackers were delaying the passengers’ assault from reaching the cockpit and that the intended target was in Washington, most likely the U.S. Capitol or White House.
The human toll
The attacks killed 2,977 victims, not counting the nineteen hijackers: 2,753 in New York, 184 at the Pentagon and aboard Flight 77, and 40 aboard Flight 93. Victims came from more than ninety countries. The dead included office workers, aircraft passengers and crew, visitors, police officers, firefighters, paramedics and military and civilian personnel at the Pentagon.
Those numbers do not contain the later medical toll. Survivors, residents, workers and responders were exposed to dust and contaminants at the World Trade Center site. Cancers, respiratory illnesses and other conditions have since been recognized and monitored through federal health programs. The historical record of 9/11 therefore extends beyond the people killed that morning.
Grounding the skies and responding
The FAA halted takeoffs and ordered aircraft in U.S. airspace to land, an unprecedented national action. International flights were diverted. At Gander and other Canadian airports, local communities received thousands of stranded passengers; DTiH’s account of the airspace closure and Operation Yellow Ribbon follows that parallel story.
President George W. Bush addressed the nation that evening. Rescue and recovery work continued at the World Trade Center and Pentagon. Congress authorized military force against those responsible and those who harbored them. The United States and allies invaded Afghanistan in October 2001, beginning the longest war in American history. The Department of Homeland Security was created, intelligence agencies were reorganized, and aviation screening and surveillance expanded.
The response also produced lasting controversy: wars in Afghanistan and Iraq, detention and interrogation practices, domestic surveillance, anti-Muslim hate crimes, and debates over security, civil liberties and executive power. Iraq was not responsible for the September 11 attacks, although the attacks helped shape the political climate in which the 2003 invasion was argued.
Investigation, memory and evidence
The National Commission on Terrorist Attacks Upon the United States examined the plot, emergency response and failures across government. Its 2004 report described institutional problems including barriers to information sharing, missed opportunities and an inability to imagine and prepare for an attack of this kind. It did not reduce the failure to a single warning or agency.
At the rebuilt World Trade Center, the National September 11 Memorial names those killed in the 2001 attacks and the 1993 bombing. The Flight 93 National Memorial and Pentagon Memorial mark the other crash sites. Annual readings of names keep attention on individuals rather than only on the scale of the event.
Why September 11 remains a turning point
The attacks compressed personal catastrophe, institutional failure and geopolitical transformation into a single morning. They altered borders and airports, military doctrine and intelligence work, architecture and emergency communications. They also generated myths and false claims, which is why primary records, official investigations and careful distinctions between evidence and inference remain essential.
Continue through the Major Historical Events archive, read about Philippe Petit’s 1974 walk between the Twin Towers, and return to the complete Today in History edition for September 11.
Sources and method. Times, flight movements, casualty figures and investigative findings were checked against the National September 11 Memorial & Museum timeline, the official 9/11 Commission Report, and the NIST World Trade Center investigation. This article avoids invented dialogue and private thoughts. It uses cautious language where later findings distinguish evidence from inference.
Written and fact-checked by the Discover Today in History editorial team. Last reviewed September 10, 2026.
