AS 11 SEPTEMBER is remembered, we look back at how events unfolded on the day itself:

Please Note: Viewers may find some of these videos disturbing and upsetting. Discretion is advised.

5.45am: Two of the 19 hijackers begin their journey at Portland International Jetport in Maine. Abdulaziz al-Omari and ringleader Mohammed Atta 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.

7.18am: A second team of five hijackers is caught on camera as they pass through security at Dulles International Airport in Washington for American Airlines Flight 77, bound for Los Angeles.

8.14am: Flight 11 is hijacked 15 minutes after take off by al-Omari and ringleader Atta and the three companions they had linked up with Waleed M al-Sheri, Satam al-Suqami, and Wail al-Sheri and heads towards New York.

8.37am: Air traffic control hears transmission from Flight 11 apparently intended for passengers in which they are told to stay quiet. With a hijack apparent, the military is notified and Two F-15s are scrambled minutes later.

8.46am: United Airlines Flight 175 is hijacked by Marwan al-Shehhi, Fayez Banihammad, Mohand al-Shehri, Hamza al-Ghamdi, and Ahmed al-Ghamdi and the plane – intended for Chicago – is headed instead to New York.

Seconds later the World Trade Centre’s North Tower is hit, killing all 92 passengers and the nine crew on board.

8.54am: American Airlines Flight 77 changes course as the hijackers, Hani Hanjour, Khalid al-Mihdhar, Majed Moqed, Nawaf al-Hazmi, and Salem al-Hazmi take control of a third aircraft.

Meanwhile, in New York, hundreds of police officers are deployed and two helicopters from the Police Department are disptached. This one captures footage from the air that was only recently released:

9.03am: United Flight 175 hits the South Tower of the World Trade Centre, killing all 65 passengers and crew on board instantly.

9.05am: President George W Bush is told: “A second plane hit the second tower. America is under attack.”

9.28am: With the authorities now aware of three hijacked aircraft a United Airlines Flight 93 is warned but by this stage the hijackers Ziad Jarrah, Ahmed al-Haznawi, Ahmed al-Nami, and Saeed al-Ghamdi have taken control of the plane.

9.37am: Flight 77 crashes into the Pentagon, killing all 64 passengers and crew, and 125 civilian and military personnel working there:

9.58am: Back in New York, the South Tower collapses less than an hour after it was hit. No one inside the building survives. About 600 people in and around the building are killed. Most of them worked at or above the impact zone:

10.03am: Flight 93 crashes in Shanksville Pennsylvania. It later emerges that passengers stormed the cockpit and attempted to overpower hijackers. This recently released video captured the moments after the plane crashed:

10.28am: Back in New York, the North Tower collapses. Most of the fatalities are at or above the impact zone. Sixteen people in stairwell B survive the building’s destruction:

2.38pm: New York Mayor Rudy Giuliani gives a press conference in which he estimates a huge loss of life from events in Manhattan:

5.20pm: 7 World Trade Centre, a 47-storey building that had sustained damage from falling debris and widespread fires, collapses:

8.30pm: On one of the darkest days in US history, president Bush addresses the nation: