How the World Trade Center Attack Happened: 9/11 Timeline & Mechanics

On September 11, 2001, 19 al-Qaeda operatives hijacked four commercial airliners, executing coordinated suicide attacks. Two struck the World Trade Center towers in New York City.

Timeline (EDT)

• 7:59 AM: AA Flight 11 (B767, Boston→LA) departs Logan.
• 8:14 AM: UA Flight 175 (B767, Boston→LA) departs Logan.
• 8:46 AM: AA 11 hits North Tower (WTC 1) — floors 93–99. 92 on board + hundreds in building killed instantly.
• 9:03 AM: UA 175 hits South Tower (WTC 2) — floors 77–85. Live TV captures impact.
• 9:37 AM: AA 77 (B757, Dulles→LA) hits Pentagon (Arlington, VA).
• 9:59 AM: South Tower collapses — 56 min after impact. Pancake collapse; dust cloud.
• 10:03 AM: UA 93 (B757, Newark→SF) crashes Shanksville, PA — passengers revolt.
• 10:28 AM: North Tower collapses — 102 min after impact.
• 5:20 PM: WTC 7 (47-story) collapses — debris fires.

Mechanics of Collapse

• Jet fuel (∼10,000 gal each) ignited multi-floor fires >800°C.
• Steel lost ~50% strength at 600°C; floor trusses sagged, pulled perimeter columns inward.
• Progressive "pancake" failure: floors stacked, momentum amplified, near-free-fall speed.
• NIST (2005) confirmed: fire-induced structural failure — no explosives.

Casualties & Aftermath

• 2,977 killed (2,753 at WTC; 184 Pentagon; 40 UA 93).
• 343 FDNY, 71 LE, 8 EMS died responding.
• Triggered: War on Terror, Afghanistan/Iraq invasions, Patriot Act, DHS, TSA, global security paradigm shift.

The attacks were planned by Khalid Sheikh Mohammed, approved by bin Laden, exploiting aviation security gaps (box cutters allowed, cockpit doors unlocked).