United Airlines Flight 175 crashes into Two World Trade Center, the south tower.
American Airlines Flight 77 crashes into the west side of the Pentagon.
Two World Trade Center, the south tower, collapses.
United Airlines Flight 93 crashes in Somerset County, Pa.
One World Trade Center, the north tower, collapses. Sept. 12, 2001
President Bush calls the Sept. 11 attacks "acts of war." The president asks Congress for $20 billion in aid.
Sept. 13, 2001
U.S. airports are reopened. Reagan National in Washington and Logan International in Boston remain closed for security reasons.
Secretary of State Colin L. Powell names Osama bin Laden as a prime suspect in the attacks. He is the first person from the Bush administration to do so.
Sept. 14, 2001
The Department of Justice releases the names of the 19 hijackers. Seven of the hijackers were trained airplane pilots.