The national memorial to United Airlines Flight 93 (search), brought down by the Sept. 11 hijackers in an open field, will carry the theme "A common field one day, a field of honor forever."

The theme was set in a mission statement approved Friday by the Flight 93 Federal Advisory Commission, which also recommended preserving about 2,200 acres of the crash site and surrounding area.

Of the 2,212 acres, 1,260 would be designated a national park and 952 would protect the spot from development.

Officials are negotiating with about 10 property owners to buy the land for the park, and they want to get easements or buy the land for the buffer.

"One hundred years from now, we want people to see the land exactly as it was on Sept. 11 (search), 2001," said Joanne Hanley, superintendent of the Flight 93 National Memorial.

The land will be purchased using a $666,000 trust fund set up by Somerset County (search) officials from money donated by the public since the crash, which killed all 40 passengers and crew on board. More donations probably will be needed.

"What's really poignant to me is this money has come from the American people," said county Commissioner Pamela Tokar-Ickes, who is also on the federal advisory commission.

Besides setting the theme, the commission developed guidelines for the memorial's design.

Information on the design competition will soon be posted on the Internet.

Registration to enter will begin Sept. 11, the third anniversary of the attacks, and end Dec. 27. After private and public review, a small number of designs will be selected as finalists. The winning design will be announced Sept. 11, 2005.

The commission has received two $500,000 grants for the design competition, from the Heinz Endowments and the John S. and James L. Knight Foundation.