Obama leads America in remembering 9/11 victims
US President Barack Obama led the nation in remembering the nearly 3,000 people who died in the September 11 attacks 15 years ago.
He observed the sombre anniversary with a moment of silence in the Oval Office at 8.46am Eastern Time - the precise moment the attacks began on a sunny day in 2001 - when a hijacked passenger plane slammed into the north tower of New York City's World Trade Center.
Afterwards, Mr Obama arrived at the Pentagon, where he laid a large wreath at the beginning of a memorial service.
The American flag was lowered to half-staff at the White House and other federal buildings.
At Ground Zero, hundreds of victims' relatives and dignitaries gathered to hear the reading of the names of the nearly 3,000 people killed, under an overcast sky that shrouded the 1,776ft-tall top of One World Trade Center, the centrepiece of the rebuilt site.
"It doesn't get easier. The grief never goes away. You don't move forward - it always stays with you," said Tom Acquaviva, of Wayne, New Jersey, who lost his son Paul Acquaviva.
Hundreds of people also attended a ceremony at the Flight 93 National Memorial in Shanksville, Pennsylvania.
The 15th anniversary arrives in a country caught up in a political campaign. Hillary Clinton and Donald Trump also followed a custom of halting television ads for the day.
While Ground Zero and the nation around it are forever marked but greatly changed since 9/11, the anniversary ceremony itself has become one of the constants in how America remembers the attacks.
Organisers planned some additional music and readings yesterday to mark the milestone year. But they were keeping close to what are now traditions: moments of silence and tolling bells, an apolitical atmosphere and the hours-long reading of the names of the dead.
"This idea of physical transformation is so real here," September 11 memorial president Joe Daniels said this week. But on this September 11 itself, "bringing the focus back to why we did all this - which is to honour those that were lost - is something very intentional".
Financial and other hurdles delayed the redevelopment of the Trade Center site early on, but now the 9/11 museum, three of four currently planned skyscrapers, an architecturally adventuresome transportation hub and shopping concourse and other features stand at the site. A design for a long-stalled performing arts centre was unveiled on Thursday.
Around the Trade Center, lower Manhattan now has dozens of new hotels and eateries, 60,000 more residents and more visitors than before 9/11.