9/11 TIMELINE: REVISITING THE SEPTEMBER 11 ATTACKS AT WORLD TRADE CENTER, PENTAGON, FLIGHT 93

5:45 a.m.: Hijackers Mohamed Atta and Abdul Aziz al-Omari board a flight at Portland International Jetport in Maine, later connecting to American Airlines Flight 11 at Boston Logan International Airport.Ads by scrollerads.com

7:49 a.m.: Flight 11 takes off.

8:15 a.m.: United Airlines Flight 175 takes off from Boston, bound for Los Angeles.

8:20 a.m.: American Airlines Flight 77 takes off from Washington Dulles International Airport.

8:24 a.m.: Atta broadcasts a message to air traffic control, “We have some planes. Just stay quiet and you will be okay.” The captain of Flight 175, United Airlines pilot Victor J. Saracini, picks up Atta’s transmission from Flight 11 and informs the Federal Aviation Administration.

8:37 a.m.: Boston’s air traffic control center alerts the Air Force’s Northeast Air Defense Sector to Atta’s message. Air National Guard jets are mobilized to follow Flight 11.

8:42 a.m.: United Airlines Flight 93 takes off from Newark International Airport.

8:46 a.m.: Flight 11 crashes into floors 93 through 99 of the north tower of the World Trade Center. Responders mobilize.

8:50 a.m.: President George W. Bush is notified of the attacks while visiting an elementary school in Florida.

8:52 a.m.: A flight attendant on Flight 175 informs a United Airlines operator that the flight has been hijacked.

8:59 a.m.: Port Authority Police Department Sergeant Al Devona orders the twin towers to be evacuated.

9:03 a.m.: United Airlines Flight 175 crashes into floors 77 through 85 of the south tower of the World Trade Center.

9:05 a.m.: Bush is informed a second plane hit the south tower.

9:12 a.m.: Passengers on Flight 77 call their loved ones to tell them the plane was hijacked.

9:37 a.m.: American Airlines Flight 77 crashes into the Pentagon.

9:42 a.m.: The Federal Aviation Administration (FAA) grounds all flights.

9:45 a.m.: The White House and Capitol are evacuated.

9:58 a.m.: Flight 93 passenger Edward P. Felt uses his cell phone to dial 9-1-1 and inform emergency operators of the hijacking.

9:59 a.m.: The south tower collapses.

10:03 a.m.: Passengers on United Airlines Flight 93 attack the hijackers aboard their plane in an attempt to seize control. The hijackers crash the plane into a field near Shanksville, Pennsylvania.

10:15 a.m.: The Pentagon’s E Ring collapses.

10:28 a.m.: The north tower collapses.

11:02 a.m.: New York City Mayor Rudolph Giuliani orders the evacuation of Lower Manhattan.

12:16 p.m.: United States airspace is closed.

12:30 p.m.: A group of survivors is found in the lower section of the North Tower’s stairwell B.

5:20 p.m.: The building at 7 World Trade Center collapses.

8:30 p.m.: Bush addresses the nation from the White House.

At the World Trade Center, 2,753 people were killed. An additional 184 died at the Pentagon and 40 were killed when Flight 93 crashed in Pennsylvania. More than 200 people have died from illnesses related to the attacks.