Sept. 11, 2001 5:45 a.m.
Hijackers Mohamed Atta and Abdulaziz al-Omari pass through airport security; 17 more hijackers soon clear their security checks at various airports.
Sept. 11, 2001 8:46 a.m.
American Flight 11 slams into floors 93-99 of the World Trade Center's North Tower.
Sept. 11, 2001 9:03 a.m.
United Flight 175 plows into floors 77-85 of the World Trade Center's South Tower.
Sept. 11, 2001 9:37 a.m.
American Flight 77 crashes into the Pentagon.
Sept. 11, 2001 9:42 a.m.
With almost 5,000 planes in the air, the FAA grounds all flights.
Sept. 11, 2001 10:03 a.m.
United Flight 93 crashes into a Pennsylvania field in Somerset County.
Sept. 11, 2001 8:30 p.m.
President Bush addresses the nation, calling the attacks "evil, despicable acts of terror" and promising "to find those responsible and bring them to justice."
Sept. 13, 2001
Congress votes to allow President Bush to use "all necessary and appropriate force" in responding to the terrorist attacks.
Sept. 17, 2001
After an unprecedented four-day closure, Wall Street reopens.
Sept. 20, 2001
During an address to Congress, President Bush promises a long, unremitting campaign against terrorism.
Sept. 21, 2001
Congress passes a $15 billion bailout for the airline industry and sets up a trust fund for compensating 9/11 victims.
Sept. 24, 2001
President Bush announces a freeze on all U.S. assets of terrorist groups, with international banks following suit.
Oct. 5, 2001
In Florida, tabloid newspaper photo editor Bob Stevens dies from inhaling anthrax.
Oct. 7, 2001
The first bombs rain down on Afghanistan's Taliban regime and its al-Qaeda allies.
Oct. 10, 2001
NBC announces that anthrax has infected anchorman Tom Brokaw's assistant, who opened the tainted letter in mid-September.
Oct. 15, 2001
Anthrax hysteria reaches Capitol Hill, where millions of spores are released from a letter mailed to Senate Majority Leader Tom Daschle.
Oct. 12, 2002
Terrorists with ties to al-Qaeda bomb the resort island of Bali, killing more than 200 people.
Oct. 23, 2002
Chechen militants storm a Moscow theater, taking some 800 people hostage. More than 120 hostages later die after officials use a toxic gas to end the siege.
March 20, 2003
The United States invades Iraq.
Dec. 13, 2003
U.S. forces capture Saddam Hussein, who is later convicted and dies by hanging on Dec. 30, 2006.
March 11, 2004
Ten bombs explode on Madrid's commuter trains, killing 190 people.
July 7, 2005
Four explosions rock London's public transportation system, killing more than 35 people.
June 7, 2006
A U.S. airstrike kills Abu Musab, the leader of al-Qaeda in Iraq.
In an audiotape, Osama bin Laden purportedly claims responsibility for an attempt to blow up a plane on Christmas Day 2009 and warns of more U.S. attacks.
May 1, 2011
U.S. forces kill bin Laden in a raid on his Pakistani compound.
For more, visit the 9/11 Memorial's interactive timeline, which includes video and audio clips.