The United Nations joined its host city, New York, in commemorating the 2,977 lives lost on 11 September 2001, when Al-Qaida terrorists hijacked four aircrafts and flew them into buildings in the United States.

Two of the planes struck the twin skyscrapers of the World Trade Center in Manhattan's financial district, while another was flown into the US military headquarters at the Pentagon outside Washington, DC. The fourth aircraft crashed into a field in Pennsylvania after passengers wrested back control from the hijackers.