Hijackers begin journey
Portland International Jetport, Maine. Two of the 19 hijackers begin their journey. The moment is caught by a security camera, as Abdulaziz al-Omari, (centre) and ringleader Mohammed Atta, (right) pass through the airport checkpoint before flying to Boston, where they will board American Airlines Flight 11 - the plane they and three companions plan to hijack.
Security, American 77
Dulles International Airport, Washington suburbs. A second team of five hijackers is caught on camera as they pass through security for American Airlines Flight 77, bound for Los Angeles. This clip shows Khalid al-Midhar and Nawaf al-Hazmi. In the past few days, both men have been placed on a watch list - but airport security do not know this.
American 11 hijacked
The hijackers stab at least two crew members and one passenger while snatching control of the jet, 15 minutes after take-off. The alarm is raised five minutes later by flight attendant Betty Ong. She uses the airphone to call American Airlines, telling them: "The cockpit is not answering. Somebody's stabbed in business class - and I think there's Mace."
Air traffic control contact the military authorities after receiving a transmission from American 11, apparently intended for the passengers: "If you try to make any moves, you'll endanger yourself and the airplane. Just stay quiet." A hijack is apparent. Two F-15s are scrambled nine minutes later (library picture, 6 Nov).
UA 175 hijacked
The pilots are killed and Mace and bomb threats are used as the hijackers take control of a second jet. At 8:58 it begins to head for New York. A passenger calls his father: "I don't think the pilot is flying the plane ... I think they intend to go to Chicago, or someplace, and fly into a building. Don't worry, Dad - if it happens, it'll be very fast."
American 11 smashes into the World Trade Center's North Tower at 440mph (700km/h). All 92 passengers and nine crew on board the Boeing 767 are killed, as are many office workers. People above the 92nd floor of the 110-storey skycraper are trapped. The plane's fuel creates a massive fireball. It travels as far down the building as the lobby level on West Street.
Fire teams at scene
Firefighters enter the lobby of the North Tower. They find windows blown out and many people with burn injuries. They begin a rescue mission, and start ascending the stairwells. By 9:00 the fire department chief is at the scene and 235 firefighters have been dispatched.
American 77 hijacked
American 77 changes course at 8:54 as the hijackers take control of a third aircraft. The Boeing 757's transponder is turned off two minutes later. Passengers begin calling loved ones to report the emergency on board - they say the hijackers used knives during their attack.
NYPD deploys hundreds
The New York Police Department raises nearly 1,000 officers to deal with the disaster. Two helicopters have been dispatched already and two police officers present in the North Tower on impact are urging people to evacuate. The Port Authority Police Department too has officers at the scene. By 9:00 they order an evacuation of all civilians in the WTC.
Evacuation is under way as United 175 hits the South Tower of the World Trade Center at 540mph (870km/h). The Boeing 767 slices through floors 77 to 85. All 65 passengers and crew die instantly. One stairwell to the upper floors remains passable, although many people climb towards to the roof, hoping for rescue there.
"A second plane hit the second tower. America is under attack," White House Chief of Staff Andrew Card tells the president. For another five to seven minutes, George W Bush remains in the classroom at Emma E Booker Elementary School, in Sarasota, Florida, where he is visiting children during a reading lesson.
Bush's first statement
In his first, brief, statement on the multiple attacks on the United States, the president promises to: "Conduct a full-scale investigation to hunt down and to find those folks who committed this act. Terrorism against our nation will not stand." His immediate thought is to return to Washington from Florida.
VP in the bunker
Fears that American 77 is approaching the White House see the Secret Service evacuate Vice President Dick Cheney to the bunker. Later, Mr Cheney advises the president against an immediate return to the capital. The vice president (right) is pictured here in the White House Operations Center on 9/11.
American Airlines Flight 77 crashes into the Pentagon at full throttle, killing all 64 passengers and crew, and 125 civilian and military personnel at work in the building. Located just outside Washington DC, the five-sided complex is the nerve-centre of the US military and one of the largest office buildings in the world.
South Tower collapses
Less than an hour after it was hit, the 110-storey building takes 10 seconds to collapse. No one left inside survives. Clouds of choking dust and debris are strewn across southern Manhattan. About 600 people in and around the building are killed. Most of them worked at or above the impact zone.
United 93 crashes
Fire-scorched trees mark the spot in Shanksville, Pennsylvania, where United 93 hit the ground. Hijackers crash the plane when faced with losing control over it. During the flight, passengers and crew phoned loved ones and were told of the attacks in New York. This knowledge led to a desperate fightback.
North Tower collapses
The North Tower collapses with the same shocking speed as the South Tower. Around 1,400 people die in and around the building. Like the South Tower, most of the fatalities are at or above the impact zone. Sixteen people in stairwell B survive the building's destruction. In this clip the BBC's Stephen Evans reports from the scene.
US airspace closed
By around 12:30 US airspace is closed for the first time in the nation's history. All non-emergency civilian aircraft are grounded. Tens of thousands of people are stranded at airports around the country.
President returns to DC
The President arrives in Washington, over nine hours after he left Florida. He has spent much of the day travelling between various safe locations on Air Force One. Here, he is shown talking to the vice president by phone.
Addressing the nation from the White House, President Bush sums up one of the darkest days in US history. He tells the nation: "These acts of mass murder were intended to frighten our nation into chaos and retreat, but they have failed."
Bush meets with NSC
After the president's sombre address to the nation, he holds a meeting of the National Security Council. President Bush makes it clear that he intends to punish those groups who had planned and executed the attacks - as well as any nations which harbour them.