A crane hoisted the final pieces of the spire atop One World Trade Center on Thursday. When fully installed, the building will stand a symbolic 1,776 feet high, making it the tallest building in the Western Hemisphere.

Construction crews applauded as the spire, draped in an American flag, began heading skyward at midday on its way to the roof. It will temporarily sit on a platform at the top of the trade center until installed at a later date.

The 408-foot, 800-ton spire will also serve as a television broadcast facility. The raising of the spire was scheduled for Monday but was postponed due to inclement weather.

The tower is the primary building of the new complex at the site of the September 11, 2001 attacks. It will be one of four skyscrapers designed as a memorial for the fallen Twin Towers and the nearly 3,000 people killed.

Formerly called the Freedom Tower, One World Trade Center is estimated to cost more than $3 billion. It will have 3 million square feet (278,000 square meters) of office space, an observation deck, and various shops and restaurants. The skyscraper is due to open next year.

The work comes just more than a week after surveyors, inspecting a Lower Manhattan site of a planned Islamic community center, found a piece of landing gear believed to be from one of the planes that was destroyed in the Twin Towers' attacks. It was discovered wedged between a mosque site and another building, just three blocks from Ground Zero. A search concluded that no remains were found, the city medical examiner's office said.

The timing of the delivery of the spire coincides with the second anniversary of the death of Osama bin Laden, the organizer of the September 11, 2001 attacks.