What to Know
The president will mark Sunday's anniversary by observing a moment of silence in the privacy of the White House residence at 8:46 a.m.
Nearly 3,000 people were killed in New York City, Pennsylvania and at the Pentagon when hijacked airliners slammed into those areas.
"The core values that define us as Americans. The resilience that sustains us."
Hailing the values and resilience that he says both define and sustains Americans, President Barack Obama on Saturday honored the nearly 3,000 souls that were lost in the Sept. 11 terrorist attacks, as well as the bravery of survivors and the emergency personnel who responded, and the work of scores of others who have labored since to keep the homeland safe.
In his weekly radio and Internet address, Obama said that while so much has changed in the years since 9/11, it's important to remember what has stayed the same.
"The core values that define us as Americans. The resilience that sustains us," he said on the eve of the 15th anniversary of one of the nation's darkest days.
He said the terrorists' goal is to frighten Americans into changing how they live, but "Americans will never give in to fear."
"We're still the America of heroes who ran into harm's way, of ordinary folks who took down the hijackers, of families who turned their pain into hope," Obama said.
Nearly 3,000 people were killed in New York City, Pennsylvania and at the Pentagon when hijacked commercial airliners were slammed into all three locations in attacks that were planned and carried out by the al-Qaida terrorist group. Al-Qaida leader Osama bin Laden was killed nearly a decade later by U.S. forces during a May 2011 raid on his Pakistani hideout that Obama authorized.
Obama noted in his address that the terrorist threat has evolved since Sept. 11 "as we've seen so tragically from Boston to Chattanooga, from San Bernardino to Orlando," cities that suffered headline-grabbing, terrorist-linked, fatal shootings.
He pledged that the U.S. will stay relentless against terrorism from al-Qaida and the Islamic State group, which is spreading its mayhem across the Middle East and the West.
Obama will mark Sunday's anniversary by observing a moment of silence in the privacy of the White House residence at 8:46 a.m. EDT, when American Airlines Flight 11 crashed into the north tower of the World Trade Center, before delivering remarks at a Pentagon memorial service.