The makers met victims' families to ensure the film was sensitive

Half will go to the World Trade Center Memorial Foundation, building a $500m (�270m) memorial on the site.

The film, starring Nicolas Cage, tells the true story of two police officers trapped in the rubble of the Twin Towers. It opens in the US on 9 August.

Stone promised sensitivity, after victims' relatives expressed concerns.

Five percent of receipts from 9 to 13 August will be shared equally by three charities: Tuesday's Children, which helps children who lost a parent; the Tribute WTC Visitor Center, due to open this summer; and the New York Police and Fire Widows' and Children's Benefit Fund.

The World Trade Center Memorial Foundation is due to build two reflecting pools on the footprints of the original towers.

Its acting president, Joseph Daniels, said: "It's our sacred obligation to remember the innocent victims and honour the sacrifice of the many brave individuals who gave their lives in the September 11 attacks.

"This contribution will help ensure that the memory of those heroes lives on through the World Trade Center Memorial."

Ordeal

Cage and Crash star Michael Pena play police officers John McLoughlin and William Jimeno.

The men were in a group of five officers who entered the South Tower shortly before it collapsed. The other three were killed.

The pair were trapped for 22 hours before being rescued, and are thought to be the last two survivors brought out of the rubble.