People gathering at the "Tribute in Light" in Lower Manhattan, New York, on Wednesday.
The annual tribute, which comprises 88 searchlights, was lit two days ahead of the 14th anniversary of the Sept 11, 2001, terrorist attacks yesterday.
The memorial honours "those who were lost, as well as those who worked so hard to get our city through that terrible trial", according to the Municipal Art Society of New York, which presented the tribute for 10 years.
Now handled by the 9/11 Memorial Museum, the lights of the display are shot into the sky from the roof of the Battery Parking Garage in Morris Street, and can be seen for more than 95km on a clear night.
An anniversary ceremony was held at the Memorial Plaza at the World Trade Center at 8.39am.
Six moments of silence were observed to mark when the World Trade Center towers fell, when the Pentagon was attacked and when the hijacked United Airlines Flight 93 crashed in Pennsylvania on that fateful day 14 years ago, killing 2,977 people.