10:00 A.m.
10:00: Moments after the South Tower fell, FDNY Battalion Chief Joseph Pfeifer (inside of North Tower) said on the radio the order to all firemen, at least twice, "Evacuate the building".
10:01: The FAA Command Center advises FAA headquarters that an aircraft had seen Flight 93 "waving his wings," the hijackers' efforts to defeat the passengers' counterattack.
10:02: Communicators with the Vice President in the security bunker begin receiving reports from the Secret Service of an inbound aircraft — presumably hijacked — heading toward Washington. This is Flight 93.
10:02: CNN announces that the Sears Tower in Chicago has been evacuated.
10:03 (approximately): The National Military Command Center learns from the White House of Flight 93's hijacking.
10:03:11: United Airlines Flight 93 is crashed by its hijackers and passengers at 583 mph (926 km/h, 272 m/s, or 509 knots), due to fighting in the cockpit 80 miles (129 km) southeast of Pittsburgh in Somerset County, Pennsylvania. Later reports indicate that passengers had learned about the World Trade Center and Pentagon crashes on cell phones and at least three were planning on resisting the hijackers; the resistance was confirmed by Flight 93's cockpit voice recording, on which the hijackers are heard making their decision to down the plane before the passengers succeed in breaching the cockpit door. The 9/11 Commission believed that Flight 93's target was either the United States Capitol building or the White House in Washington, D.C.
10:05: Andrea Mitchell, reporting on NBC from outside the Pentagon, reports that Osama bin Laden may have been involved in the attacks.
10:05: CNN's headlines read: "SOUTH TOWER AT WTC COLLAPSES."
10:05: The IDS Center in Minneapolis is evacuated.
10:07: NBC reports for the first time that the South Tower of the World Trade Center has collapsed. Prior to this time they have said only that a section of the building has fallen away.
10:07: NEADS, controlling the only set of fighters over Washington, first learns of the hijacking of Flight 93, 4 minutes after it actually crashed.
10:08: Air Traffic Control System Command Center in Herndon reports to FAA headquarters that Flight 93 may be down near Johnstown, Pennsylvania; at 10:17 the Command Center concludes it is so.
10:10: Part of the west side of the Pentagon collapses.
10:10: NEADS emphatically tells fighter pilots over Washington, "Negative clearance to shoot."
10:10 to 10:15 (approximately): Vice President Cheney, unaware that Flight 93 has crashed, authorizes fighter aircraft to engage the inbound plane, reported to be 80 miles (129 km) from Washington, based not on radar (from which it has disappeared) but speed and trajectory projections.
10:13: Thousands are involved in an evacuation of the United Nations complex in New York.
10:13 to 10:22: The 9/11 Commission's estimated arrival of Flight 93 over Washington had it not crashed in Pennsylvania.
10:14 to 10:19: A lieutenant colonel at the White House repeatedly relays to the NMCC that the Vice President has confirmed that fighters are cleared to engage inbound aircraft if they can verify that the aircraft was hijacked.
10:18: NBC reports that Yasser Arafat, Chairman of the Palestine Liberation Organization (PLO) has denied complicity in the attacks and is appalled by them.
10:20: President Bush, aboard Air Force One, tells Vice President Cheney that he has authorized a shootdown of aircraft if necessary.
10:23: The Associated Press reports a car bomb has exploded outside the State Department in Washington, D.C. This and several other reports of terrorist acts in the capital are quickly found to be false.
10:24: Two men who were being evacuated through the underground shopping mall below the South Tower when it collapsed on them are able to climb up through thirty feet of debris to safety.
10:28:22: The North Tower of the World Trade Center collapses. Due to the destruction of the gypsum-encased stairwells on the impact floors (most skyscraper stairwells are encased in reinforced concrete), no one who was above the impact zone in the North Tower escapes the collapse. The Marriott Hotel, located at the base of the two towers, is also destroyed. The second collapse is also viewed live on television and heard on radio. The North Tower collapses 1 hour, 42 minutes after the impact of Flight 11, meaning the building had burned during the whole duration of the attacks.
Several long-distance videos of the collapse, such as CNN, were able to notice that, after the cloud of dust had partially cleared away, a portion of the building was still standing. It appeared to be the lower half of the northwest corner column of the North Tower, which, like a spire, grew larger and had more structure still standing near the bottom. The portion rose to a fairly good height considering the collapse around it, as it appeared to rise nearly forty stories off the ground. This piece remained standing for a few seconds after the initial collapse before it also came down.
10:31: NORAD first communicates the Vice President's shootdown authority to NEADS.
10:35: Air Force One, carrying the president, turns for Barksdale Air Force Base in Bossier City, Louisiana.
10:37: Associated Press reports that officials at the Somerset County airport confirm that a large plane has crashed in western Pennsylvania. CNN's Aaron Brown passes along reports that a 747 is "down" in Pennsylvania. He stresses these reports are unconfirmed. He also, in the confusion, reports another plane heading for the Pentagon.
10:37: The Mall of America in Bloomington, Minnesota, is evacuated and closed.
10:39: Another hijacked jumbo jet is claimed to be headed for Washington, D.C. F-15s are scrambled and patrol the airspace above Washington, D.C. while other fighter jets sweep the airspace above New York City. They have orders, first issued by Vice President Cheney and later confirmed by President Bush, to shoot down any potentially dangerous planes that do not comply with orders given to them via radio. Eventually, the aircraft is revealed to be a medevac helicopter on its way to the Pentagon.
10:41: NBC News confirms that a plane has "gone down" in Somerset County. The earlier unconfirmed statements about an incident at the State Department in Washington, D.C. are reported as false.
10:43: CNN reports that a mass evacuation of Washington, D.C. and New York has been started. A few minutes later, New York mayor Rudy Giuliani orders an evacuation of Lower Manhattan.
10:49: Fox News Channel is the first of the United States news networks to implement a news ticker at the bottom of its screen for supplementary information about the attacks. CNN adds one at 11:11, and MSNBC adds one at approximately 2:00 pm. All three cable networks have used a news ticker continuously in the years since (and many local television stations have followed suit).
10:50:19: Five stories of part of the Pentagon collapse due to the fire.
10:53: New York's primary elections are canceled.
10:53: Defense Secretary Donald Rumsfeld orders the US Military placed at DEFCON 3, for the first time since the Yom Kippur War in 1973.
Read more about this topic: Timeline For The Day Of The September 11 Attacks, Significant Events