Investigation Summary
The hijacking began at approximately 08:14 EDT when the aircraft failed to respond to instructions to climb. The hijackers used mace or pepper spray to clear the cabin and forced passengers toward the rear. Flight attendants Betty Ong and Madeline Sweeney provided critical intelligence via airphone, identifying the hijackers' seat numbers and reporting that the cockpit had been breached. At 08:24, Mohamed Atta accidentally transmitted two messages to Air Traffic Control while attempting to address the passengers, confirming the hijacking. The aircraft's transponder was turned off at 08:21, making it difficult for controllers to track the flight as it deviated toward New York. The aircraft struck the North Tower at 466 mph (750 km/h) between floors 93 and 99, severing all escape routes for those above the impact zone.
Final Conclusions
The destruction of the aircraft was the result of a deliberate act of terrorism. The subsequent collapse of the North Tower 101 minutes after impact was caused by structural damage from the crash and the intense heat of the resulting jet-fuel-fed fires, which weakened the building's steel support system.
Video Analysis
No video analysis linked for this case file yet.
Systems & Failure Modes
Transponder
The device was manually turned off by the hijackers to hide the aircraft's altitude and identity from secondary radar.
Cockpit Door
The door was breached by the hijackers; at the time, cockpit doors were not reinforced against forced entry.
Airphone
Onboard telephone system used by flight attendants to provide the first specific details of the hijacking to the ground.
Interesting Facts
- 01It was the deadliest plane crash in history, including ground fatalities.
- 02The impact was captured on video by filmmaker Jules Naudet.
- 03The aircraft was carrying approximately 10,000 gallons of jet fuel at the time of impact.
- 04Lead hijacker Mohamed Atta had trained as a pilot in the United States specifically for this mission.
- 05The flight was only about 15% full, with 81 passengers in a cabin designed for many more.
Safety Actions & Advisories
Reinforced Cockpit Doors
The FAA mandated the installation of hardened, bulletproof cockpit doors on all commercial airliners to prevent unauthorized access.
TSA Establishment
The Transportation Security Administration was created to oversee all airport security screening, replacing private contractors.
Flight Deck Officer Program
Legislation was passed to allow trained pilots to carry firearms in the cockpit for self-defense.