The following is a detailed timeline (Irish time) of how the deadly terror attacks in New York and Washington unfolded yesterday:
13.56 - An aircraft hits one of the towers of the World Trade Centre in New York, leaving a giant hole in the building's facade. Thick smoke trails into the sky from the tower's upper floors.
14.14 - A second aircraft hits the second of the World Trade Centre's twin towers, sparking a violent explosion, seen live on television.
14.30 - A first toll counts at least six dead and 1,000 injured.
14.40 - President Bush, speaking while on a visit Sarasota, Florida, calls the blasts "an apparent terrorist attack". He orders "a full-scale investigation to hunt down and to find those folks who committed these acts", and says he will immediately return to Washington.
14.50 - In Washington, the White House is evacuated, shortly after the evacuation of the Pentagon (US defence department) in suburban Washington.
14.53 - The US State Department headquarters in the centre of Washington is evacuated.
14.53 - Two explosions rock the Pentagon and smoke pours out of the building. "It's a bomb, get out," says a Pentagon spokesman. An early toll says seven are injured.
15.00 - US officials at the Federal Aviation Administration (FAA) order the cancellation of all commercial flights inside the US.
15.05 - One of the World Trade Centre's two towers collapses in a huge cloud of smoke and dust following an explosion. 15.28 - The second tower of the World Trade Centre collapses like a house of cards, sending tons of debris into the surrounding streets. A huge cloud of dust blankets lower Manhattan.
15.42 - US Secretary of State Colin Powell, in the Peruvian capital Lima, cancels a trip to Colombia, due to have taken place yesterday.
15.50 - United Airlines announces in Paris that one of its planes, a Boeing 737, crashed into the World Trade Centre.
15.55 - An FBI official announces that a hijacked plane is headed towards the Pentagon. In Washington, there is traffic chaos and pedestrians flee from the area around the White House.
16.17 - New York City Mayor Rudolph Giuliani asks all New Yorkers to evacuate the southern tip of Manhattan.
16.33 - FAA officials announce that they have lost control of one or several planes.
16.34 - A Boeing 747, travelling from Newark to San Francisco, crashes in western Pennsylvania. United Airlines says afterwards that one of its planes has crashed in Pennsylvania, without specifying a cause for the crash.
16.38 - American Airlines announces it has lost contact with two of its aircraft, with 156 people aboard.
16.53 - Train traffic is suspended between Boston and Washington.
17.00 - An American Airlines jet crashes into the Pentagon, hitting the building at the second floor.
17.31 - United Airlines announces in Paris the loss of a second aircraft, a Boeing 767 (UA Flight 175).
17.50 - New York's National Guard is activated to reinforce New York City police in evacuating the city and maintaining order, Mr Giuliani says.
18.30 - Mr Bush, in Shreveport, Louisiana, says that US armed forces are on worldwide high-alert status and promises to "hunt down and punish" those responsible for the attacks in New York and Washington.
18.50 - Washington, DC, Mayor Anthony Williams declares a state of emergency in the US federal capital for an undetermined length of time.
19.00 - All US stock markets are closed for the afternoon, the US Securities and Exchange Commission announces.