9/11 TIMELINE: from multiple sources you can verify:
7:59: American Airlines Flight 11, a Boeing 767, departs late from Logan International Airport bound for Los Angeles, California. Five hijackers are aboard.
8:13: The last radio communication is made from Flight 11. What is believed to be Atta's voice says, "Nobody move. Everything will be OK. If you try to make any moves, you'll endanger yourself and the airplane. Just stay quiet." The flight path begins to stray away from the scheduled one and moves southwards.
8:14: United Airlines Flight 175, another fully-fueled Boeing 767, carrying 56 passengers and nine crew members, departs from Boston Logan airport, also bound for Los Angeles. Five hijackers are aboard.
8:19: Betty Ong, a flight attendant on Flight 11  alerts American Airlines of a hijacking in progress via an airphone.
8:20: The Federal Aviation Administration's Boston Center flight controllers decide that Flight 11 has probably been hijacked. American Airlines Flight 77, a Boeing 757 with 58 passengers and six crew, departs from Washington Dulles International Airport
8:21 Flight 11's transponder signal is turned off but the plane remains on radar screens. (Prior to the 9/11 Commission's report, news organizations reported this time as 8:13 or immediately thereafter.)
8:24 Flight 11 makes a 100-degree turn to the south heading toward New York City. A radio transmission comes from Flight 11: "We have some planes. Just stay quiet, and you'll be okay. We are returning to the airport."
8:25: Boston Center flight controllers alert other flight control centers regarding Flight 11; however, NORAD is not yet alerted.
8:34: Boston Center contacts Otis Air National Guard Base at Cape Cod, through the FAA's Cape Cod facility, on the hijacking of Flight 11.
8:37: Flight 175 confirms sighting of hijacked Flight 11 to flight controllers, 10 miles (16 km) to its south.
8:37:52: Boston Center control notifies NEADS (Northeast Air Defense Sector), the northeast sector of NORAD, of the hijacking of Flight 11, the first notification received by the military, at any level, that American 11 had been hijacked. The controller requests military help to intercept the aircraft.
8:42: United Airlines Flight 93, a Boeing 757, takes off with 37 passengers and seven crew members from Newark International Airport, bound for San Francisco International Airport
8:42: The FAA's New York Center requests information about Flight 11 over the radio. Flight 175 responds: "Ah, we heard a suspicious transmission on our departure out of Boston, ah, with someone, ah, it sounded like someone keyed the mikes and said ah everyone stay in your seats."
8:44: Flight attendant Amy Sweeney, aboard Flight 11, reports by telephone to American Airlines Flight Services Office in Boston, "Something is wrong. We are in a rapid descent . . . we are all over the place." When asked to look out the window, she says, "We are flying low. We are flying very, very low. We are flying way too low." Seconds later she says, "Oh my God we are way too low," before the call ends.
8:46: Two F-15 fighter jets are scrambled from Otis Air Force Base in Massachusetts, intended to intercept flight 11. Because Flight 11's transponder is off, United States Air Force pilots do not know which direction to travel to meet the plane. NEADS spends the next several minutes watching their radar screens in anticipation of Flight 11 returning a radar contact.
8:46:40: Flight 11 crashes at roughly 490 mph (790 km/h or 425 knots) into the north side of the North Tower of the World Trade Center, between floors 94 and 98
8:50: NEADS is notified that a plane has struck the World Trade Center as they continue to locate the flight on radar.
8:51: A flight controller at the FAA's New York Center notices that Flight 175 had changed its transponder code twice four minutes earlier; he tries to contact the flight.
8:51 to 8:54 (approx.): Hijacking begins on Flight 77.
8:53: The F-15s at Otis Air Force Base are airborne. Still lacking an intercept vector to Flight 11 (and not aware that it has already been crashed)
8:54: Flight 77 deviates from its assigned course to Los Angeles, turning south over Ohio. Two minutes later, its transponder is turned off, dissappears from Indianapolis Center radar until 9:05AM and is initially believed to have crashed.
9:03:11: Flight 175 crashes at about 590 mph (950 km/h) into the south side of the South Tower, banked between floors 78 and 84
9:03: FAA's New York Center notifies NORAD (NEADS) of the hijacking of Flight 175.
9:04 (approximately): The FAA's Boston Air Route Traffic Control Center stops all departures from airports in its jurisdiction (New England and eastern New York State).
9:06: The FAA bans takeoffs of all flights bound to or through the airspace of New York Center from airports in that Center and the three adjacent Centers — Boston, Cleveland, and Washington. This is referred to as a First Tier groundstop and covers the Northeast from North Carolina north and as far west as eastern Michigan.
9:08: The FAA bans all takeoffs nationwide for flights going to or through New York Center airspace. ABC reports later that the Port Authority of New York and New Jersey, the agency that runs the New York-area airports, asked the FAA for permission to close down the New York Center airspace.
9:13: The F-15 fighters from Otis Air Force base leave military airspace near Long Island, bound for Manhattan.
9:23: Flight 93 receives warning message text from United Airlines flight dispatcher: "Beware any cockpit intrusion- Two a/c [aircraft] hit World Trade Center."
9:24: The FAA notifies NORAD's Northeast Air Defense Sector about the suspected hijacking of Flight 77. The FAA and NORAD establish an open line to discuss Flight 77, and shortly thereafter Flight 93.
9:25: The Otis-based F-15s establish an air patrol over Manhattan.
9:26: The FAA bans takeoffs of all civilian aircraft regardless of destination — a national groundstop (the first such grounding in American history). All military bases in the United States are ordered to increase its threat conditions to Delta status.
9:28: Hijackers storm the cockpit on Flight 93 and take over the flight. The entry of the hijackers is overheard by flight controllers at Cleveland.
09:30: Fighters are scrambled from Langley AFB to fly CAP over DC.
9:33 to 9:34: Tower supervisor at Reagan National Airport tells Secret Service operations center at the White House that "an aircraft [is] coming at you and not talking with us," referring to Flight 77. The White House is about to be evacuated when the tower reports that Flight 77 has turned and is approaching Reagan International Airport.
9:34: The FAA's Command Center relays information concerning Flight 93 to FAA headquarters.
9:35: Flight 93 reverses direction over Ohio and starts flying eastwards.
9:37:46: Flight 77 crashes into the western side of the Pentagon
9:40: Video teleconference in White House Situation Room begins with the physical security of the President, the White House, and federal agencies. They are not yet aware of the Pentagon crash.
9:45: United States airspace is shut down. No civilian aircraft are allowed to take off, and all aircraft in flight are ordered to land at the nearest airport as soon as possible.
9:49: The FAA Command Center at Herndon suggests that someone at FAA headquarters should decide whether to request military assistance with Flight 93. Ultimately, the FAA makes no request before it crashes.
9:57: Passenger revolt begins on Flight 93.
9:59:04: The South Tower of the World Trade Center collapses, 55 minutes 51 seconds after the impact of Flight 175
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.
10:03: United Airlines Flight 93 is crashed by its hijackers southeast of Pittsburgh in Somerset County, Pennsylvania. The exact time is subject to some dispute — a report on seismographic data readings by Won-Young Kim and Gerald R. Baum puts the time of impact at 10:06:05
10:03 (approximately): The National Military Command Center learns from the White House of Flight 93's hijacking.