In pictures: Pentagon before and after 9/11
The 9/11 hijackers struck at the heart of the US military when they crashed American Airlines Flight 77 into the world-famous Pentagon building.
All 64 passengers and crew died, as well as 125 civilian and military personnel at work in the building. GeoEye satellite images here show the Pentagon before and immediately after the 11 September attacks and how it looks 10 years on.6 April 2000
The five-sided, five-storey building, built on swamp and wasteland, was completed in 1943 and is one of the largest office buildings in the world. It is the headquarters of the US Department of Defense. Some 23,000 military and civilian employees work at the building just outside Washington DC.12 September 2001
American Airlines Flight 77 was the third of four hijacked aircraft to crash. It hit the Pentagon at 0937 on 11 September 2001, disintegrating in a ball of flame as it ploughed through three sections, or rings of the building. The aircraft hit the west side of the Pentagon - which had been undergoing renovation at the time, meaning some offices were not occupied. Officials say this, and the completed improvements, saved lives by enabling more people to escape.22 August 2011
The areas damaged by the attack and areas which had not undergone renovation were completely rebuilt at a cost of $500m. A memorial to those who lost their lives in the attacks was opened in 2008.