Attack on the World Trade Center | Attack on the Pentagon
Anatomy of terrorist attacks | How the buildings most likely collapsed

World Trade Center facts:

Size: Seven buildings, including the twin 110-floor towers.
The others: a 47-story office building, two nine-story office buildings, an eight-story U.S. Customs office and a 22-story hotel.
Height: The twin towers were each 1,350 feet tall.
Cost: Roughly $1.25 billion.
Rentable Space: 12 million square feet; some 1,200 companies and organizations leased space.
Workers: Roughly 50,000 people in both towers.
Visitors: On average, 90,000 tourists and business visitors each day.

Boeing 767 Flight 11 carrying 92 people, Flight 175 carrying 65 people; Capacity: 255 Overall length: 159 feet, 2 inches Wingspan: 156 feet, 1 inch Maximum speed: 414 mph Weight: 176,200 lbs. (empty) Fuel capacity: 13,900 gallons

Sources: Skilling Ward Magnusson Barkshire; Port Authority of New York and New Jersey: Knight Ridder Newspapers; New York Times; The Associated Press