Neither candidate had any political events scheduled for Thursday. The 2001 attacks transformed the nation in many ways, and one is that every anniversary since has found those holding or seeking office struggling for ways to appropriately pay homage.
McCain was briefly speaking at a ceremony near the Shanksville crash site, alongside other dignitaries and relatives of the 40 passengers and crew who were killed there. Investigators believe passengers rushed the cockpit of United Airlines Flight 93 to thwart terrorists' plans to use that plane as a weapon like the others.
In the afternoon, in New York, Obama and McCain were to visit ground zero together for a somber, silent wreath-laying in the pit that marks the largest loss of life in the attacks.
That appearance is to be followed by another in the evening at a Columbia University forum to discuss their views on public service.
Obama's only other planned outing Thursday was lunch in New York with former President Clinton.
A joint statement from the campaigns announcing their decision to visit ground zero together said they wanted to do so in thanks for all emergency responders who served during and after the attacks as well as the military troops still defending the nation.
"We will put aside politics and come together to renew that unity, to honor the memory of each and every American who died, and to grieve with the families and friends who lost loved ones," the statement said.
The two candidates last appeared together in June at the funeral of NBC newsman Tim Russert, where they sat next to each other at the family's request.