They were joined by loved ones of those who died.
The first phase of the 2,200-acre park being built near Shanksville, 75 miles southeast of Pittsburgh, was dedicated on the 10th anniversary of 9/11.
The park memorializes the 40 passengers and crew who stormed the cockpit of United Flight 93 that dark day and brought down the jet in an abandoned coal field just 20 minutes before it would have reached what investigators later determined was the hijackers' destination - the Capitol in Washington.
But almost 11 years later, funds raised are still $14 million shy of the $76 million total needed to complete the park.
Of that $14 million, $4 million is expected to come from the federal government, while $10 million is needed from private donors to cover construction costs of a visitors' center, a 93-foot tall "tower of voices" containing 40 aluminum wind chimes, and 40 memorial groves of red maple trees.
Headlining the star-studded event Tuesday at the Newseum in Washington were former Presidents George W. Bush and Bill Clinton, along with House Speaker John Boehner. All spoke passionately about the selfless actions of the passengers and crew and urged donors to contribute in their memory, listeners said.
"It's important to always honor courage, and I think the acts of those on 93 will go down as one of the most courageous acts in the history of the United States," Bush said in his remarks Tuesday, according to the New York Times. The event was closed to news media.
Of funds raised for the memorial thus far, $30 million has come from the private sector and $32 million from government sources, including $18 million from the state of Pennsylvania, the largest single donor.
Most of the nongovernment money is the result of small checks written by 100,000 individual donors in all 50 states and 20 countries, said Neil Mulholland, president of the National Parks Foundation, which supports the National Park Service and is handling fund-raising for the Flight 93 park.
Mulholland said pledges were still coming in from Tuesday's fund-raiser, in amounts that he said would push the night's final tally well above $2 million.
The event grew out of a conversation between Clinton and Boehner last September at the park.
Officials briefing Clinton on the status of the project mentioned the shortfall in funding. People who were present that day said Clinton was surprised, given that 9/11 memorials at the World Trade Center site and the Pentagon were fully funded.
The Democratic former president turned to the Republican House speaker and said, in essence, "We're going to get this done," said Patrick White, president of the Families of Flight 93.
And in a small way, White said, that moment reflected the spirit that the families want remembered. "What happened on 9/11 was a new paradigm, the people on the plane said 'we're not going to take it sitting down,' " said White, whose cousin, Louis "Joey" Nacke of New Hope, Pa., was on Flight 93.
The Tuesday event was held near the Newseum's permanent exhibit on 9/11, which includes the largest intact piece of fuselage from the Boeing 757 jet.
"I think part of the story that is lost is that plane's intended target was the U.S. Capitol," said Mulholland. "There was a joint session of Congress scheduled . . . and tours were fully booked. Had they not acted, our government would have been taken out."
Among the Pennsylvania dignitaries who attended the Washington event were Sens. Bob Casey, a Democrat, and Pat Toomey, a Republican; former governors Ed Rendell, a Democrat, and Tom Ridge, a Republican; and U.S. Reps. Mark Critz, a Democrat, and Bill Shuster, a Republican.
Rendell, who as governor ensured that the park received significant state funding, said he was confident that the private fund-raising drive would reach its goal so the project could be completed.
"Seven million is not that much, considering what the passengers on that flight did," Rendell said in an interview on Wednesday, suggesting that the federal government might commit more funds.
To the several family members who attended, the evening was both emotional and empowering, said White, who has devoted nearly a decade of work to the memorial project even as he grieves. He has been deeply involved in the park development, including leading the land acquisition negotiations.
"To see this commitment is quite gratifying and gives us a degree of confidence that the end is in sight," he said. "For me, it will be hearing the 40 voices reunited by the bells in the tower. Then I will know I am done."
Contact Amy Worden at 717-783-2584 or email@example.com or follow @inkyamy on Twitter.
To donate to the Flight 93 National Memorial fund go to the National Parks Foundation website, www.honorflight93.org.