9/11 terror attacks 20th anniversary: Timeline of events

Saturday marks the 20th anniversary of the 9/11 terror attacks on the United States that left nearly 3,000 people dead and triggered a chain of events that reshaped the world. It plunged the West into costly wars in Iraq and Afghanistan -- the second one ending just last month. Here's the timeline of events on that clear blue September morning.

American Airlines Flight 11, a Boeing 767 flying from Boston to Los Angeles with 92 people on board -- including five hijackers -- crashes into the North Tower of the World Trade Center at 8:46 am. The impact leaves a giant hole and thick smoke rises from the upper floors.

Seventeen minutes later, with television audiences around the world gasping in horror, United Airlines Flight 175, also a Boeing 767 flying Boston-Los Angeles, this time with 65 people on board -- including five hijackers -- hits the World Trade Center's South Tower. Nearly an hour after the hit, the building came down in a huge cloud of smoke and dust. The North Tower followed several minutes later.

American Airlines Flight 77, a Boeing 757 headed from Washington's Dulles airport to Los Angeles with 64 people on board -- including five hijackers -- smashes into the west facade of the Pentagon just outside the US capital. All commercial flights in the United States to land as quickly as possible

United Airlines Flight 93, a Boeing 757 traveling from Newark to San Francisco with 44 people on board -- including four hijackers -- crashes into a field near Shanksville, Pennsylvania, after passengers and crew who had learned about the other attacks fought with the hijackers.

2,753 people were killed in the twin towers with the remains of hundreds of victims remaining unidentified for years. Even as late as this week the remains of two who died were identified from DNA matches. In the other two crashes, 224 people died.