A jet airliner is lined up on one of the World Trade Center towers in this Sept. 11, 2001, file photo.
American Airlines Flight 11 takes off from Logan International Airport in Boston with 76 passengers, 11 crew members, and 5 hijackers.
United Airlines Flight 175 takes off from Logan with 51 passengers, 9 crew members, and 5 hijackers.
Two flight attendants on Flight 11, Betty Ong and Madeline Amy Sweeney, tell American Airlines about the hijacking; the airline calls the FBI.
American Airlines Flight 77 takes off from Dulles International Airport near Washington carrying 53 passengers, 6 crew members, and 5 hijackers.
United Airlines Flight 93 takes off from Newark International Airport, carrying 33 passengers, 7 crew members, and 4 hijackers.
Flight 11 hits the north tower of the World Trade Center.
Chief of Staff Andy Card whispers into the ear of President George W. Bush to give him word of the plane crashes into the World Trade Center, during a visit to the Emma E. Booker Elementary School in Sarasota, Fla.
President George W. Bush, who is reading to second graders at Booker Elementary School in Sarasota, Fla., is told that the World Trade Center has been hit by a plane.
Flight 175 hits the south tower.
President Bush announces on television: "Two airplanes have crashed into the World Trade Center in an apparent terrorist attack on our country."
Vice President Dick Cheney is evacuated to a bunker under the White House.
Flight 77 crashes into the Pentagon.
The Federal Aviation Administration grounds all flights over and to the continental United States.
Evacuations begin in the White House and the Capitol.
President Bush leaves Sarasota for Barksdale Air Force Base in Louisiana.
The south tower collapses.
Firefighters and emergency personnel investigate the fatal crash scene of Flight 93 in Shanksville, Pa.
After passengers on Flight 93 try to regain control, hijackers crash the plane in a field near Shanksville, Pa.
The north tower collapses.
From a firehouse, Mayor Rudolph W. Giuliani calls NY1 and tells people to evacuate Lower Manhattan. The city asks for help from the National Guard.
President Bush arrives at Barksdale; he leaves at 1:15 p.m.
At a news conference, Mayor Giuliani says, "The number of casualties will be more than any of us can bear ultimately."
President Bush arrives at the U.S. Strategic Command at Offutt Air Force Base in Nebraska; he leaves 90 minutes later.
Three rescue workers walk away from the crash site at the Pentagon in Arlington, Va., in this Sept. 11, 2001, file photo.
7 World Trade Center collapses.
President Bush arrives at the White House.
President Bush addresses the nation, calling America "the brightest beacon for freedom and opportunity in the world." He vows to direct full resources to finding and bringing to justice those behind the "evil acts" of Sept. 11.