The commemoration of the 15th anniversary of 9/11 began at ground zero Sunday with a moment of silence and tolling bells at 8:46am, the time when a terrorist-piloted plane slammed into the World Trade Center's north tower, reports the AP. After the silence, victims' relatives began reading the names of the nearly 3,000 people killed when four hijacked aircraft hit the trade center, the Pentagon, and a Pennsylvania field. It was the deadliest terror attack on American soil. President Obama will speak at an observance at the Pentagon. Hundreds of people also are expected at a ceremony at the Flight 93 National Memorial in Shanksville, Pennsylvania. Democratic presidential nominee Hillary Clinton and Republican rival Donald Trump are attending the anniversary ceremony at the World Trade Center.
Family members of those lost on Sept. 11 earlier began arriving at ground zero, with some going to National September 11 Museum, which is open only to victims' families until Sunday afternoon, when the public will be allowed to enter. As it has every year, the remembrance will mainly focus on the reading of the names of those killed in the attacks. Organizers have planned some additional music and readings to mark the milestone anniversary at ground zero. But they are keeping traditions that have made the ceremony a constant in how America remembers Sept. 11, even as ground zero and the nation changes. "This idea of physical transformation is so real here," Sept. 11 memorial President Joe Daniels said. But on this Sept. 11 itself, "bringing the focus back to why we did all this—which is to honor those that were lost—is something very intentional." (Read more 9/11 attacks stories.)