In emotional speeches, former Presidents George W. Bush and Bill Clinton paid tribute to the 40 passengers and crew who were killed when United Airlines Flight 93 crashed in a field in Shanksville, Pa., on September 11, 2001.
Retelling the story of how those on board fought back against the hijackers, Bush called their bravery the "first counteroffensive of the war on terror."
"The most likely target of the plane was the United States Capitol," Bush said. "We'll never know how many innocent people might have been lost, but we do know this: Americans are alive today because the passengers and crew of Flight 93 chose to act, and our nation will be forever grateful."
The former presidents joined Vice President Biden, Interior Secretary Ken Salazer and House Speaker John Boehner (R-Ohio) for the dedication of the Flight 93 memorial a day before the 10th anniversary of the attacks.
Clinton, saying the he was "aghast" to find out that $10 million more was needed to finish the memorial, will set up a fundraising drive.
"Speaker Boehner and I have already volunteered to do a bipartisan event in Washington," Clinton said. "Let's get the show on the road."
The event largely stressed the heroism and sense of unity sparked by 9/11, and Clinton praised both of his Oval Office successors and the Congress.
"I think we should also thank President Bush and those who served with him, Vice President Biden and President Obama, those who served with them, for keeping us from being attacked again," Clinton said.
"Speaker Boehner, I thank you and the members of the Congress who are here and who have been in the Congress for the last 10 years, trying to respond to the findings of the 9/11 Commission and improve our ability to secure our homeland."
The speakers only brushed against politics when Bush touched briefly on foreign policy, encouraging the nation to avoid isolationism.
"We have a duty to remain engaged in the world -- 9/11 proved that the conditions in a country on the other side of the world can have an impact on our own streets," Bush said. "It may be tempting to think that it doesn't matter what happens to a child in Africa or a villager in Afghanistan, but the temptation of isolation is deadly wrong."