Times of Sept. 11 Attack, WTC Collapse

NEW YORK (AP) -- The beginning of the end of the World Trade Center was at 8:46.26 a.m., when hijacked American Airlines flight 11 smashed into the north face of the 110-story north tower.

The end came 1 hour, 42 minutes, 5 seconds later when that tower fell in a heap of rubble and cement dust.

In the interim on Sept. 11, 2001, United Airlines flight 175 crashed into the south face of the south tower at 9:02.54, dooming it to collapse 56 minutes, 10 seconds later.

Seven hours after that, at 5:20.33 p.m., the fire-damaged, 48-story building 7 also fell, completing the destruction of the complex.

Although initial reports varied from one reporting agency to another, the precise moments eventually were established by a seismograph at Columbia University's Lamont Doherty Earth Observatory in Palisades, N.Y., 21 miles north of the World Trade Center.

Lamont-Doherty also recorded the impact, according to the Richter Scale that measures earthquakes. Each full digit represents a 10-fold increase in a tremor's magnitude.

Here are the Eastern Daylight times, duration of impact and Richter scale magnitude: