The seventh anniversary of the Sept. 11 attacks is supposed to bring the heated presidential race to a screeching halt. But just for a day.

Republican John McCain and Democrat Barack Obama were appearing together twice Thursday and agreed to suspend all TV ads critical of each other to commemorate the day terrorists forced four airplanes to crash into the World Trade Center towers in New York City, a field in Shanksville, Pa., and the Pentagon in Washington, killing nearly 3,000 people.

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.