A pair of white beams lifting into the air captured the admiring gaze of crisp-suited elected officials and blue-jean-clad construction workers.

The silent crowd, which included top state leaders such as Gov. Mark Sanford and Senate President Pro Tem Glenn McConnell, gathered Friday morning at Boeing Co.'s North Charleston campus to watch cranes hoist the delicately suspended 1.5-ton beams 100 feet over their heads. The scene was framed by an industrial web of steel that will make up the company's 1.2 million-square-foot final assembly building.

From behind the fanfare, Mike Pace, the project director for general contractor BE&K/Turner Joint Venture, observed with folded arms.

The process stripped of all this ceremony "would be about 10 times faster," he said. Then he added softly, "But it's a time to pause for celebration."

For a few hours, the dust settled at the North Charleston construction site for a milestone event: placing the last major bits of steel onto the building's 18,000-ton structure.

The $750 million building, scheduled to open in July, will house nearly 4,000 workers as they piece together 787 Dreamliner jets before handing them over to commercial airline customers.

"This is the most quiet I've heard this site in the last 10 months and three days," said Marco Cavazzoni, Boeing's vice president and general manager of final assembly and delivery, standing at a podium.

Behind him stood a sea of bobbing maroon, yellow and orange construction hats. Hundreds of workers attended the event -- a portion of the more than 2,700 construction workers who have been trained to work on the site so far.

Since late November, they've labored to clear 150 acres of dense forestland, scrape away 2.4 million cubic yards of muddy earth and haul in sturdy sand to take its place.

Construction workers then skewered the ground with 158 reinforced pilings before building the skeletal framework skyward.

They've done the jobs at a frenzied pace, putting in 11 hours on a typical workday. Construction crews report to the site seven days a week, reserving weekends for special projects.

Workers continued to pour concrete into a 35,000-square-foot area as the first elected officials trickled in for Friday's event.

All this work has taken place safely. Sometime around noon on Thursday, workers collectively logged 1 million hours without a lost-time accident.

Within two months, workers will fully enclose the building, disappearing inside to complete the usual interior finishings. And in March, they'll hand over the keys to Boeing officials, who will outfit the interior with its own equipment.

The building itself will cover 11 acres of Boeing's 250-acre North Charleston campus. One of the adjacent fuselage plants could fit entirely inside.

On Friday, the dangling white beams appeared to float until three platforms of workers rose to their height. Workers pushed them into place and secured them with exactly 16 bolts.

A clustering of workers beneath the scene looked no bigger than ants.

Reach Katy Stech at 937-5549.