Presidents attend Flight 93 National Memorial dedication on 9/11 (VIDEO)

Family members of the 40 passengers and crew died on United Airlines Flight 93 when it crashed into a Pennsylvania field have attended a moving ceremony at the newly dedicated Flight 93 National Memorial in Shanksville.

On Sunday, President Barack Obama and First Lady Michelle Obama arrived by helicopter around noon for a wreath-laying ceremony at the memorial, to applause and chants of "U-S-A, U-S-A." 

The president laid a wreath of 40 white roses on the Flight 93 Memorial — a wall of 40 marble slabs, each inscribed with the name of a victim of the crash of United Airlines Flight 93, the WSJ reports. They then shook hands, hugged and spoke with victims' family members, many of them tearful. 

One man yelled, "Thank you for getting bin Laden!" according to the LA Times.

Obama called the actions of those aboard Flight 93 — who stormed the cockpit of their hijacked jetliner, preventing the Al Qaeda terrorists at the controls of the aircraft from hitting their target — as among the most courageous in U.S. history.

The plane went down 20 minutes by air from Washington, where the hijackers are believed to have been planning to hit the Capitol or the White House.

At the earlier ceremony marking the 10th anniversary of the attacks, the Flight 93 Memorial was dedicated with speeches by former presidents George Bush and Bill Clinton.

According to the AP:

Nearly 5,000 people listened as the names of the passengers and crew who were killed were read aloud while bells tolled. Afterward, a children's choir sang as those in the crowd — including family members, first responders, politicians and more than 1,000 other private citizens — listened intently.

AFP reports that the names of Flight 93 passengers and crew were read out in alphabetical order, from German wine merchant Christian Adams to flight purser Deborah Jacobs Welsh, to Toshiya Kuge of Osaka, Japan whose mother uttered his name.

The 1,500-acre park that houses the memorial has cost $52 million to date, but is expected to cost another $10 million to complete, a point not lost on Doug Mink, a high school teacher from Cincinnati, according to the Washington Post.

Mink remarked to the Post that the country's flagging economy was lately of more concern to many Americans than national security. 

"We need to get America going again. I don’t feel like we’re at the forefront of things anymore. For example, this memorial still needs $10 million to be finished. If the economy was better, that would not be a problem."

A private ceremony will be held Monday, while the park remains closed to the public, at which remains of the victims will be buried.