In an attack orchestrated by al Qaeda leader Osama bin Laden, 19 men hijacked four passenger planes on September 11, 2001.

Two of the planes were intentionally crashed into the World Trade Center towers in New York. Another crashed into the Pentagon. The fourth crashed in a field near Shanksville, Pennsylvania. Nearly 3,000 people were killed.

These photos show how the day unfolded.

First picture:
This image taken from video, American Airlines Flight 11 is seen seconds before crashing into the north tower of the World Trade Center at 8:46 a.m. ET. It was the first plane that hit the World Trade Center. Flight 11 took off from Boston and was scheduled to fly to Los Angeles.