WASHINGTON -- First Lady Michelle Obama and her predecessor, Laura Bush, will travel to Shanksville, Somerset County, to mark the ninth anniversary of the Sept. 11 terrorist attacks.

The visit to the memorial site of the Flight 93 crash, which honors the 40 passengers and crew who challenged terrorist hijackers aiming the plane for Washington, comes one year before the scheduled completion of a permanent memorial there for the attack's 10th anniversary.

Interior Secretary Ken Salazar and Gov. Ed Rendell also are scheduled to attend, the National Park Foundation --- the charity arm of the National Park Service --- announced today.

"We are deeply honored to welcome First Lady Michelle Obama, Mrs. Laura Bush and all of our guests to this important event," Neil Mulholland, the president of the National Park Foundation, said in a news release. "Their show of support honors the lives and memories of these 40 heroes and everyone we lost on Sept. 11, and serves as a valuable reminder of how important this memorial is to preserve and share their story."

The ceremony will be held at the Western Overlook portion of the site, where a temporary visitors' center opened last month.

The National Park Foundation is helping to raise $30 million in private donations for the $58.4 million permanent memorial.

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