Boeing Chairman of the Board Jim McNerney, center, announced a $20 million donation to the Kennedy Center in Washington on Wednesday. (Gary Cameron/Reuters)

Boeing announced Wednesday that it will give $20 million to the Kennedy Center to support its $100 million expansion project.

Boeing chairman W. James McNerney Jr. told Kennedy Center Board Chairman David M. Rubenstein of the gift before sitting down with Rubenstein for a question-and-answer session at the Economic Club of Washington. The 460 business leaders in attendance offered a collective “wow” upon hearing the news.

“We at Boeing have supported the Kennedy Center. We’ve been proud to do it,” McNerney said. “Your leadership has made a huge difference.”

McNerney was appointed to the Kennedy Center board in May. The gift is the second that has been made to the capital campaign. Rubenstein made the lead gift of $50 million.

Deborah F. Rutter, the Kennedy Center’s president, called the donation “inspiring.”

“It ensures the success of the project overall. It helps to encourage others to step forward,” Rutter said.

Designed by Steven Holl, the expansion will add 60,000 square feet of rehearsal, classroom, performance and event space in three pavilions and underground. It will transform the landscape to the south of the art center’s white marble building by adding a grove of trees, a sloping lawn that can be used as an informal amphitheater and a reflecting pool.

A ceremonial groundbreaking took place in December and construction was expected to begin in March. But design issues surfaced during the approval process. A revised design that moves a wharf-life concert space from the water to land was approved this month. Officials said they hope construction will begin in the fall and that the project will be completed in the fall of 2018, about 15 months behind schedule.

Boeing’s gift is one of the largest corporate donations made to the arts center. The final budget of the revised plan has not been released, although officials expect the changes to make the cost more than $100 million.

The project will be funded by private donations. Rubenstein, chief executive and co-founder of the Carlyle Group, is also the president of the Economic Club. He thanked McNerney for the donation and noted the company’s long history of supporting the center.

“And for all who are going to be future guests,” he told the audience, “I hope this sets a precedent.”