Construction workers applauded as the upright spire began heading skyward at midday Thursday on its way to the roof.
The spire's temporary home will be a platform at the top of the trade center. When it's fully installed, at a later date, it will soar to a symbolic 1,776 feet.
The 408-foot spire will be used as a world-class broadcast antenna.
The new tower is at the northwest corner of the trade center site. The area is well on its way to reconstruction with the 72-story Four World Trade Center and other buildings.