The first plane, an American Airlines Boeing 767 carrying 81 passengers and 11 crew from Boston to Los Angeles hits one of the World Trade Centre towers. An estimated 25,000 were in this tower at the time. A 767 is worth between US$80m and US$100m.
The second plane, an American Airlines Boeing 757, carrying 58 passengers and six crew from Washington to Los Angeles, hits the other World Trade Centre tower. Again, an estimated 25,000 people were in this tower at the time. Some began jumping from the windows of burning offices to the streets below.
A second Boeing 767, carrying 56 passengers and nine crew from Boston to Los Angeles, crashes into the Pentagon, causing explosions and destroying five storeys. Twenty six casualties are taken to hospital in Virginia and seven in a critical condition with burns were taken to a Washington hospital. An estimated 20,000 people are evacuated from the Pentagon.
The White House is evacuated.
The World Trade Centre's south tower collapses.
A United Airlines Boeing 747 carrying 38 passengers and seven crew, flying from Newark to San Francisco, crashes 80 miles south-east of Pittsburgh.
All transatlantic flights into the US are diverted to Canada. Air Canada suspends all flights soon after.
The World Trade Centre's north tower collapses.
Downtown Manhattan was evacuated under a veil of smoke and ash. A major gas leak is reported.
Islamic Jihad, Hamas, and the Democratic Front for the Liberation of Palestine have all denied liability.