The September 11 attacks began when four commercial airliners were hijacked and used as weapons in coordinated suicide missions, targeting symbols of US economic and military power.
The timeline of events shows two jets struck the Twin Towers in New York, a third hit the Pentagon in Arlington County, and a fourth crashed in rural Pennsylvania after passengers resisted, according to contemporary accounts.
Mohamed Atta led the team that flew the first plane into the North Tower, while other hijacker-pilots included Marwan al-Shehhi, Hani Hanjour and Ziad Jarrah, as reported in investigative findings.
The day left nearly three thousand dead, with one widely cited tally listing 2,977 victims and comprehensive summaries noting 2,996 total deaths including 19 hijackers, according to available sources.
The Federal Aviation Administration ordered a nationwide ground stop and diverted many international flights, an action described in official timelines and aviation reports.
Air defenses were scrambled after notification from air traffic control, and senior officials later authorized shootdown orders, though those measures did not prevent the four crashes, according to post‑attack inquiries.
Investigators quickly attributed the operation to al-Qaeda. The group and its leader Osama bin Laden were identified as responsible by intelligence inquiries and later public statements from US agencies.
Aftermath Effects And Institutional Responses
The attacks triggered the US Global War on Terror and an overseas military campaign to remove the Taliban from power in Afghanistan and to dismantle al-Qaeda safe havens, as recorded in policy summaries.
Domestically, Congress and the administration created new security structures and laws, including a cabinet-level Department of Homeland Security and expanded surveillance and law enforcement powers under post-attack legislation.
Authorities opened the largest criminal inquiry in US history to trace planning and support networks, while commissions and engineering agencies examined intelligence failures and the structural collapses of the towers.
Public health and legal consequences followed. Toxic dust at the World Trade Center led to long-term illnesses among first responders and residents, prompting the World Trade Center Health Program and compensation efforts.
Economic damage included major market shocks and concentrated losses in transport and financial sectors. Rebuilding at the World Trade Center site produced a memorial, museum and the new One World Trade Center skyscraper.
The attacks also produced enduring legal and diplomatic disputes, including litigation over alleged foreign links, detainee policies, and prolonged prosecutions of those accused of planning the plot.
