"We made it. Not to our goal, not to the finish line. Certainly not any semblance of closure, but nevertheless, we made it to the next milestone of our journey," said Gordon Felt, whose brother, Edward Felt, was one of the 40 passengers and crew who died when the plane crashed into a field near rural Shanksville, about 105km southwest of Pittsburgh.

The government intends to have the first phase completed by Sept. 11, 2011 - the 10th anniversary of the terrorist attacks. Felt called it a "Herculean effort" to reach the groundbreaking - acquiring land from some private owners had been contentious and some critics said the design itself honored the terrorists.

Gov. Ed Rendell said the memorial will tell of "ordinary citizens bound by a sense of urgency and action that changed the history of the world." Flight 93 was traveling from Newark, New Jersey, to San Francisco when it was hijacked with the likely goal of crashing it into the White House or Capitol, the 9/11 Commission found.

With Beamer's words, passengers rushed down the airliner's narrow aisle to try to overwhelm the hijackers after learning of the coordinated attacks. The commission concluded that the hijackers downed the plane as the hostages revolted. It was the only one of four hijacked planes that day that did not take a life on the ground.

Salazar said the victims did something profoundly democratic which the terrorists could never understand: They took a vote on whether to fight for control of the plane. "These heroes did not cow down to fear," he said. Felt said his brother and the other 39 victims "knew they were fighting evil personified that day."

Sarah Wainio, 22, of Catonsville, Maryland, was one of the 40 who turned a shovel. She was 14 when her sister, Honor Elizabeth Wainio, died aboard the plane. She called the event "huge" not just for the victims' relatives, but for the entire country and even the world so they can know the heroic story.