8:45 a.m. (all times are EDT): A hijacked passenger jet, American Airlines Flight 11 out of Boston, Massachusetts, crashes into the north tower of the World Trade Center, tearing a gaping hole in the building and setting it afire.
9:03 a.m.: A second hijacked airliner, United Airlines Flight 175 from Boston, crashes into the south tower of the World Trade Center and explodes. Both buildings are burning.
9:17 a.m.: The Federal Aviation Administration shuts down all New York City area airports.
9:21 a.m.: The Port Authority of New York and New Jersey orders all bridges and tunnels in the New York area closed.
9:30 a.m.: President Bush, speaking in Sarasota, Florida, says the country has suffered an "apparent terrorist attack."
9:40 a.m.: The FAA halts all flight operations at U.S. airports, the first time in U.S. history that air traffic nationwide has been halted.
9:43 a.m.: American Airlines Flight 77 crashes into the Pentagon, sending up a huge plume of smoke. Evacuation begins immediately.
9:45 a.m.: The White House evacuates.
9:57 a.m.: Bush departs from Florida.
10:05 a.m.: The south tower of the World Trade Center collapses, plummeting into the streets below. A massive cloud of dust and debris forms and slowly drifts away from the building.
10:08 a.m.: Secret Service agents armed with automatic rifles are deployed into Lafayette Park across from the White House.
10:10 a.m.: A portion of the Pentagon collapses.
10:10 a.m.: United Airlines Flight 93, also hijacked, crashes in Somerset County, Pennsylvania, southeast of Pittsburgh.
10:13 a.m.: The United Nations building evacuates, including 4,700 people from the headquarters building and 7,000 total from UNICEF and U.N. development programs.
10:22 a.m.: In Washington, the State and Justice departments are evacuated, along with the World Bank.
10:24 a.m.: The FAA reports that all inbound transatlantic aircraft flying into the United States are being diverted to Canada.
10:28 a.m.: The World Trade Center's north tower collapses from the top down as if it were being peeled apart, releasing a tremendous cloud of debris and smoke.
10:45 a.m.: All federal office buildings in Washington are evacuated.
10.46 a.m.: U.S. Secretary of State Colin Powell cuts short his trip to Latin America to return to the United States.
10.48 a.m.: Police confirm the plane crash in Pennsylvania.
10:53 a.m.: New York's primary elections, scheduled for Tuesday, are postponed.
10:54 a.m.: Israel evacuates all diplomatic missions.
10:57 a.m.: New York Gov. George Pataki says all state government offices are closed.