The Park Service will spend the next several years working to suppress the spread.
Winter schedules for National Parks have also been announced.
The former land owner claims the land is worth much more than he was paid.
The National Park Service awarded a contract for the construction of the new Flight 93 Visitor's Center.
Mother travels from Japan to Pennsylvania to honor her son who died on flight 93.
Organizers say everything that happened at the Flight 93 ceremonies couldn't have happened without a special group of people.
Family members and volunteers light up the Flight 93 Memorial.