SHANKSVILLE — The site where United Airlines Flight 93 crashed after passengers confronted hijacking terrorists during the Sept. 11 attacks almost a decade ago is being marked by a gigantic boulder.

Over the years, relatives of the victims have talked with the National Park Service and other memorial planners about how to mark the impact site in Western Pennsylvania, and the use of a large boulder was suggested, park service superintendent Keith Newlin said Saturday at a meeting of the Flight 93 Advisory Commission, which is responsible for providing recommendations on the planning, construction and management of the Flight 93 National Memorial.

A committee of the Families of Flight 93, an association of victims’ relatives, approved the idea, and the 17-ton boulder was recently moved into place by New Enterprise Stone and Lime, which is building the entrance road from Route 30 and the ring road at the memorial, Newlin said.

“It was a challenge,” Newlin told the Daily American newspaper, of Somerset.

“At one point I suggested a smaller rock, but the New Enterprise foreman said, ‘They deserve this stone,’ and the crew did not give up. They should be commended.”