On the morning of the second Tuesday in September, two airliners crashed into the World Trade Center towers in New York, causing the collapse of three skyscrapers and thousands of deaths. Thick clouds of smoke filled the air and debris showered the streets as the world watched it all on live television.
Before the morning was over, two more passenger jets crashed -- one into the Pentagon in Washington, another into a field near Pittsburgh, Pennsylvania. Everyone on board the two planes was killed, along with 100 people on the ground. All air travel in the United States was halted as authorities scrambled for answers.
September 11: Chronology of terror
In-depth: Day of terror
Collapsed Trade Center towers still dangerous
2001 September 11
