The day America changed

• 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.

• 6:00 a.m.: Polls open in New York City for primary elections.

• 7:59 a.m.: American Airlines Flight 11 takes off from Boston, with Atta and Omari on board, bound for Los Angeles.

• 8:14 a.m.: United Airlines Flight 175 takes off from Boston with other hijackers on board.

• 8:20 a.m.: American Airlines Flight 77 takes off from Washington Dulles airport en route to Los Angeles.

• 8:24 a.m.: On Flight 11, Atta, trying to communicate with the cabin, mistakenly contacts air traffic control.

• 8:37 a.m.: Air traffic control reports the hijacking to the US military.

• 8:42 a.m.: United Airlines Flight 93 departs Newark, N.J., with hijackers aboard.

• 8:46 a.m.: Flight 11 crashes into the North Tower of the World Trade Center (WTC).

• 8:50 a.m.: White House Chief of Staff Andrew Card tells President George W. Bush, who's visiting a Florida elementary school, about the crash.

• 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.

• 9:03 a.m.: Flight 175 smashes into the South Tower.

• 9:31 a.m.: Bush, speaking in Florida, says the country has suffered an "apparent terrorist attack."

• 9:37 a.m.: Hijackers crash Flight 77 into the Pentagon.

• 9:42 a.m.: The FAA, for the first time in history, halts all flights in the US and orders those in the air to land.

• 9:48 a.m.: US authorities evacuate the US Capitol and the White House's West Wing.

• 9:59 a.m.: The South Tower collapses.

• 10:03 a.m.: Hijackers, trying to prevent passengers from retaking the plane, crash Flight 93 in a field southeast of Pittsburgh.

• 10:28 a.m.: The North Tower collapses.

• 10:50 a.m.: New York postpones primary elections.

• 11:02 a.m.: New York Mayor Rudy Giuliani calls for the evacuation of about 1 million people from lower Manhattan.

• 12:15 p.m.: INS puts US borders with Canada and Mexico on high alert but doesn't shut them.

• 12:30 p.m.: 14 "miracle survivors," who were shielded by a stairwell, are rescued from the fallen North Tower.

• 12:30 p.m.: The FAA says 50 flights remain in US airspace, but none report problems.

• 1:44 p.m.: Pentagon dispatches warships to protect the Eastern Seaboard.

• 4:25 p.m.: America's major stock exchanges announce they will remain closed Wednesday.

• 4:30 p.m.: Firefighters raise a flag in the wreckage of the twin towers.

• 8:30 p.m.: Bush, addressing the nation, vows to "find those responsible and bring them to justice."

• Sept. 14, 2001: Congress authorizes Bush to use all "necessary" force to prevent future terror attacks.

• 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.

• Sept. 20, 2001: Bush announces a cabinet-level Office of Homeland Security.

• Oct. 7, 2001: US launches war in Afghanistan.

• Oct. 26, 2001: Bush signs USA Patriot Act, granting authorities broad surveillance and detention powers.

• December 2001: US-led forces oust Taliban from a final refuge, Tora Bora, but Osama bin Laden is believed to have escaped to Pakistan.

• Dec. 22, 2001: British citizen Richard Reid is arrested for trying to blow up a jet with a shoe explosive.

• June 1, 2002: Bush outlines a new military doctrine that stresses the option of preemptive action against any group or nation threatening US security.

• March 20, 2003: US invades Iraq.

• Dec. 13, 2003: US forces capture Saddam Hussein.

• Feb. 5, 2003: Colin Powell tells the UN that Hussein was definitely working to create nuclear weapons.

• Feb. 2, 2004: Bush calls for an independent panel to study intelligence failures leading up to the Iraq war.

• March 11, 2004: Ten bombs go off in trains in Madrid, killing 190 people.

• April 30, 2004: Reports surface of US abuse of Iraqi prisoners at Abu Ghraib.

• July 7, 2005: Four explosions rock London's transit system, killing 52 people.

• Jan. 10, 2007: Bush announces troop surge in Iraq.

• Dec.1, 2009: President Obama announces a troop surge in Afghanistan.

• May 1, 2011: US Special Forces kill bin Laden in a raid in Pakistan.