BBC News Online looks back at the key moments of 11 September 2001 - the day on which the United States suffered the world's most devastating terrorist attack.
0845 Eastern Daylight Time (1245GMT) At the height on the New York morning rush hour American Airlines Flight 11 crashed into the north tower of the World Trade Center. It had set off from Boston en route to Los Angeles with 92 people on board.
Click here to watch amateur footage of the first attack
0903 EDT News cameras trained on the burning tower captured live the horrifying view of another passenger jet, United Airlines Flight 175, crashing into the south tower of the Trade Center causing a devastating explosion. It had left Boston for Los Angeles carrying 65 passengers and crew. It became clear that the catastrophe was not an accident.
0910 EDT In Florida President Bush was reading to children in a classroom when his chief of staff, Andrew Card, whispered news of the attacks into his ear.
The BBC's James Robbins gives the full story on America's darkest day
0920 EDT The FBI announced that it was investigating reports of planes being hijacked.
0929 EDT Rescue workers and fire marshals rushed to the foot of the World Trade Center as the upper floors blazed. On an ordinary day, 50,000 people would be working in the Trade Centre, and up to 100,000 tourists would have visited it.
Kenneth Jahanaman, a janitor at the World Trade Center, describes the moments after the buildings were hit
0930 EDT A grim-faced President George Bush declared: "We have had a national tragedy. Two aeroplanes have crashed into the World Trade Center in an apparent terrorist attack on our country."
President Bush's statement initial
0940 EDT American Airlines Flight 77, carrying 64 people from Washington to Los Angeles, crashes into the Pentagon in Washington. The nerve centre of the US military bursts into flames and a portion of one side of the five-sided structure collapses.
Eyewitnesses in New York describe the aftermath of the crashes
0945 EDT The White House and The Capitol were evacuated amid further threats.
0950 EDT All airports across the US were shut down.
Washington under fire - The BBC's Rob Watson reports
0950 EDT The south tower of the World Trade Center tower suddenly collapsed sending a massive pall of smoke across Manhattan. Many emergency workers and firefighters are crushed or trapped in the collapsing building, as well all those who could not get out of the tower.
0958 EDT An emergency despatcher in Pennsylvania received a call from a passenger on United Flight 93 who said: "We are being hijacked, we are being hijacked!"
1000 EDT United Airlines Flight 93 crashed 130km (80 miles) south east of Pittsburgh. It had been bound for San Francisco from Newark, New Jersey.
BBC correspondent Steven Evans was being interviewed live as the first tower collapsed
1025 EDT A car bomb was reported to have exploded outside the State Department in Washington.
1029 EDT The north tower of the World Trade Center collapsed adding to the devastation. In apocalyptic and chaotic scenes, thousands ran screaming from the scene. The southern part of Manhattan Island is covered in a thick layer of debris and dust.
1239 EDT President Bush made a second statement, in which he vowed to hunt down and punish those responsible.
Relatives of Mark Bingham, a passenger who died on one of the hijacked planes, tell of his mobile phone call to them moments before his plane crashed
1320 EDT President Bush left Barksdale Air Force Base in Louisiana and flew to Omutt Air Force Base in Nebraska.
1344 EDT The Pentagon deploys five battleships and two aircraft carriers along the east coast of the US to provide upgraded air defence for the New York and Washington areas.
1350 EDT Washington, DC Mayor Anthony Williams declared a state of emergency in the US federal capital.
1448 EDT New York's mayor Rudy Giuliani said the eventual death toll from Tuesday's attack may be "more than any of us can bear".
1630 EDT President Bush left Offutt Air Force Base aboard Air Force One to return to the White House in Washington.
1720 EDT A 47 storey building adjacent to the ruins of the World Trade Center collapsed.
2030 EDT President Bush addressed the nation on TV and hinted at a strong US response against the "terrorists who committed these acts and those who harbour them".
US President Bush's address to the nation