Boeing South Carolina has started powering up its first 787 Dreamliner, a critical step toward delivering the plane this spring.

The process began last week, said spokeswoman Candy Eslinger. When the inaugural installation will be done is less clear.

Getting electricity to a new airplane is “not just like you flip a switch, and the power comes on,” Eslinger said. “It’s a pretty detailed process.”

The closely monitored jet remains in Position 3, which despite its name is the fourth of five spots in the final assembly building in North Charleston.

Position 3 is also where the mechanical and hydraulic systems are installed and tested and where certain interior components — pieces that passengers will see and touch — are installed, Eslinger said.

Eslinger said other developments reported this week — “incorrect shimming” performed at the local aft-body manufacturing operation and an apparent request from Boeing South Carolina’s first customer, Air India, for a $1 billion discount for delivery delays — would not affect the planned second-quarter delivery.

“We’re still on schedule,” she said.

Just behind the first plane, two other partially assembled Dreamliners continue to come together.

As production ramps up, so, too, has the headcount at the plant. More than 5,900 people — mostly Boeing employees but including some contractors — now work at the company’s campus at Charleston International Airport.