â€¢ 5:45 a.m. EDT: Hijackers Mohammed Atta and Abdulaziz al-Omari pass through airport security in Portland, Maine, and board a flight for Boston. Over the next 90 minutes, 17 other hijackers clear security at three other Eastern airports.
â€¢ 6:00 a.m.: Polls open in New York City for primary elections.
â€¢ 8:14 a.m.: United Airlines Flight 175 takes off from Boston with other hijackers on board.
â€¢ 8:24 a.m.: On Flight 11, Atta, trying to communicate with the cabin, mistakenly contacts air traffic control.
â€¢ 8:37 a.m.: Air traffic control reports the hijacking to the US military.
â€¢ 8:46 a.m.: Flight 11 crashes into the North Tower of the World Trade Center (WTC).
â€¢ 8:55 a.m.: Occupants of the unhit WTC's South Tower are told not to evacuate. The building is secure. Then, minutes later, the New York Port Authority initiates an evacuation.
â€¢ 9:03 a.m.: Flight 175 smashes into the South Tower.
â€¢ 9:31 a.m.: Bush, speaking in Florida, says the country has suffered an "apparent terrorist attack."
â€¢ 9:37 a.m.: Hijackers crash Flight 77 into the Pentagon.
â€¢ 9:48 a.m.: US authorities evacuate the US Capitol and the White House's West Wing.
â€¢ 9:59 a.m.: The South Tower collapses.
â€¢ 10:03 a.m.: Hijackers, trying to prevent passengers from retaking the plane, crash Flight 93 in a field southeast of Pittsburgh.
â€¢ 10:28 a.m.: The North Tower collapses.
â€¢ 10:50 a.m.: New York postpones primary elections.
â€¢ 12:30 p.m.: 14 "miracle survivors," who were shielded by a stairwell, are rescued from the fallen North Tower.
â€¢ 12:30 p.m.: The FAA says 50 flights remain in US airspace, but none report problems.
â€¢ 1:44 p.m.: Pentagon dispatches warships to protect the Eastern Seaboard.
â€¢ 4:25 p.m.: America's major stock exchanges announce they will remain closed Wednesday.
â€¢ 4:30 p.m.: Firefighters raise a flag in the wreckage of the twin towers.
â€¢ 8:30 p.m.: Bush, addressing the nation, vows to "find those responsible and bring them to justice."
â€¢ Sept. 14, 2001: Congress authorizes Bush to use all "necessary" force to prevent future terror attacks.
â€¢ Sept. 18-Oct. 9, 2001: Letters containing anthrax spores are mailed to several media offices and two US senators, killing five people and infecting 17 others.
â€¢ Sept. 20, 2001: Bush announces a cabinet-level Office of Homeland Security.
â€¢ Oct. 7, 2001: US launches war in Afghanistan.
â€¢ Oct. 26, 2001: Bush signs USA Patriot Act, granting authorities broad surveillance and detention powers.
â€¢ Dec. 22, 2001: British citizen Richard Reid is arrested for trying to blow up a jet with a shoe explosive.
â€¢ June 1, 2002: Bush outlines a new military doctrine that stresses the option of preemptive action against any group or nation threatening US security.
â€¢ March 20, 2003: US invades Iraq.
â€¢ Dec. 13, 2003: US forces capture Saddam Hussein.
â€¢ Feb. 2, 2004: Bush calls for an independent panel to study intelligence failures leading up to the Iraq war.
â€¢ March 11, 2004: Ten bombs go off in trains in Madrid, killing 190 people.
â€¢ April 30, 2004: Reports surface of US abuse of Iraqi prisoners at Abu Ghraib.
â€¢ July 7, 2005: Four explosions rock London's transit system, killing 52 people.
â€¢ Jan. 10, 2007: Bush announces troop surge in Iraq.
â€¢ Dec.1, 2009: President Obama announces a troop surge in Afghanistan.
â€¢ May 1, 2011: US Special Forces kill bin Laden in a raid in Pakistan.