One of the lasting stories of heroism from the September 11th terrorist attacks is of United Airlines Flight 93. It was the fourth jetliner commandeered by hijackers that day. It crashed in Pennsylvania, apparently because its passengers kept their attackers from striking a fourth target.

Sometime after take-off on the morning of September 11, 2001, the 40 passengers and crewmembers of United Airlines Flight 93, heading from Newark, New Jersey to San Francisco, suddenly became part of the worst terrorist attack on American soil.

Hijackers took over their plane, and some passengers managed to call home to alert family members.  Through those phone calls they learned that other terrorists had also seized three American jetliners in Boston and outside Washington -- then crashed those planes into the World Trade Center towers and the Pentagon.

Investigators believe the hijackers planned to fly the fourth plane to the nation's capital, possibly striking the U.S. Capitol building or the White House.

But before they could do so, the plane crashed in a field in Somerset County, Pennsylvania, near the town of Shanksville, about 104 kilometers southeast of Pittsburgh.

Some of the passengers had indicated they planned to fight back against their attackers.

The National Park Service has unveiled the design it chose for a memorial honoring the victims of Flight 93.

The winning design, created by Paul Murdoch Associates, was literally one in a thousand. 

The memorial will include a "Tower of Voices" -- containing 40 wind chimes, each producing a different scale and pitch to represent the silent "voices" of the victims.

A pedestrian walkway will lead to a bowl-shaped area, lined with maple trees, where visitors can stop for quiet reflection.

The path continues toward the actual point of impact, referred to as the "Sacred Ground."

Family members will be allowed to cross a special walkway to stand on that spot, where wildflowers will grow.

One family member, Dorothy Garcia, says the memorial will provide inspiration for all Americans facing hard times.

"I think it's going to be what people need. This country is hurting for a lot of reasons, and it's a place where people can go and get some healing." 

Carole O'Hare also says the victims' sacrifice must not be forgotten.

"This is part of our American history that is a must-see, it will give you an inspirational feeling to go there, because these people did something so beyond what anyone would expect a human person to do, and I think the American people should go there, should honor these heroes."

There is no date set for the actual groundbreaking. Organizers have chosen September 11, 2011, the 10th anniversary of the attacks, as the target date for completion.