Americans will return Wednesday to the grim task of commemorating the worst act of domestic terrorism in U.S. history, the day Islamist fundamentalists seized four airliners and killed nearly 3,000 people in a disaster known simply as 9/11.
Every year since then, the nation has mourned the victims of the Al Qaeda attacks, which felled both towers of New York's World Trade Center as well as the Pentagon. A fourth jetliner crashed into a Pennsylvania field when passengers tried to retake control from the hijackers.
This year's commemoration comes as the United States weighs military action against Syria.
In New York, the ceremony will be held at the 2-year-old memorial plaza at the site of the former World Trade Center. Relatives will read the names of those who died when the hijacked jets crashed into the towers, the Pentagon and the field near Shanksville, Pa.
At the Flight 93 National Memorial in Shanksville, Wednesday's ceremony will include the traditional bell-ringing and wreath-laying.
The Pentagon plans a Wednesday morning ceremony for victims' relatives and survivors of the attack there, with a wreath-laying and remarks from Defense Secretary Chuck Hagel and other officials, as well as an afternoon observance for Pentagon workers.
Americans will mark the day as a National Day of Service and Remembrance, a tradition begun in 2002 as a way to honor the spirit of cooperation that marked the deadly day and its aftermath. In 2009, Congress made Sept. 11 an official national day.