The events of 9/11 made an indelible mark in U.S. history.  Included below is a timeline  showing the unfolding of events on that fateful day. 

7:59 a.m.- American Airlines Flight 11 takes off from Boston.

8:13 a.m.- American Airlines Flight 11 is hijacked.

8:14 a.m.- United Airlines Flight 175 takes off from Boston.

8:43 a.m.- United Airlines Flight 175 is hijacked.

8:46 a.m.- American Airlines Flight 11 out of Boston, traveling at 470 mph,  crashes into the north tower of the World Trade Center with an estimated 10,000 gallons of fuel. 

8:55 a.m.- President Bush is notified of the first crash and replies, “What a horrible accident.”

9:02 a.m.-  United Airlines Flight 175 hits the south tower of the World Trade Center and explodes.

9:06 a.m.- President Bush is notified of the second crash, but remains in the school classroom in Florida where he is doing a photo-op for his educational policies.

9:16 a.m.- United Airlines Flight 93 is hijacked.

9:38 a.m.- American Airlines Flight 77 crashes into the Pentagon.

9:40 a.m.- For the first time in U.S. history, all flight operations in U.S. airports are cancelled.

10:05 a.m.- The south tower of the World Trade Center collapses.

10:10 a.m.- United Airlines Flight 93 crashes in Somerset County, Pennsylvania, southeast of Pittsburgh.

10:28 a.m.- The north tower of the World Trade Center collapses from the top down.

1:27 p.m.- A state of emergency is declared by the city of Washington, D.C.

1:44 p.m.- The Pentagon announces that five warships and two aircraft carriers will leave the U.S. Naval Station in Norfolk, Virginia, to protect the East Coast from further attack.

5:20 p.m.- The 47-story building seven of the World Trade Center complex collapses.