Panetta said the people on the plane "responded with selflessness, determination, and tremendous courage. And at the cost of their own lives, made the fateful decision to fight back, and in so doing, they successfully prevented an attack on the United States Capitol."
"This is the final resting place of American patriots," he said.
Panetta walked down to the wooded area where the plane crashed and met with relatives of people who were on the plane. The park is in a rural area about 75 miles southeast of Pittsburgh, but some visitors find it so moving that they have made repeat visits.
"I've been here in the dead of winter before," said Sue George, of Ridgeley, W.Va., adding that she loves that the names of each of the victims is inscribed on a wall of large, white marble tablets. The wall is aligned with the flight path of the plane. George also noted that the 2,200-acre site, which was once a strip mine, is now filled with beautiful views, hills covered in wildflowers and trees.
"It still feels almost wild. Which I think is the best thing ever," she said. "It's not a sad place anymore. It's our way of saying 'thank you.'"
Some first-time visitors were also moved by the site.
"I'm glad it's being protected. We need to honor these people," said Mike McClain, of Rockwood, Mich., speaking of the passengers who gave their lives to thwart the terrorists.
More and more people are visiting the memorial, according to the National Park Service, and officials hope to break ground on a visitor center next spring, and complete more tree plantings and new walkways. That phase is scheduled to be completed by 2014.
A third phase, which could cost $5 million or more, will include a learning center and a tower at the entrance with 40 wind chimes. Price estimates for the whole project have ranged from $67 million to $76 million.
At the current pace, more than 1,000 bus groups will visit the park this year, almost double the number in 2011, said King Laughlin, vice president of the Flight 93 National Memorial Campaign. More than 200,000 people are expected to visit this year.