A group made up of relatives of those killed aboard United Flight 93 on Sept. 11, 2001, announced Tuesday that it had agreed to buy a 903-acre tract to be part of a permanent memorial near Shanksville, Pa.

The land is owned by PBS Coals Inc., a company in Somerset, Pa., that previously mined the site. The company will also donate the 27 acres closest to the crash site. Both parcels will eventually be transferred to the National Park Service, which is overseeing the creation of the memorial.