Christopher Kubasik, currently the president and chief operating officer of Lockheed Martin, will become the company’s chief executive. (Jeffrey MacMillan/Capital Business)

Stevens said he plans to remain chairman of the Bethesda-based aerospace and defense contractor through 2013. He told reporters that he will turn 61 later this year and was facing a company mandatory retirement age of 65. He said he decided to step down before that in part to ensure a smooth transition.

“When I look at future challenges, I recognize they will certainly extend beyond my mandatory retirement age,” Stevens said during a morning phone call. He has been with Lockheed for 25 years, becoming president in 2000 and chief executive four years later.

Kubasik, 51, was promoted last year to serve with Stevens in a two-person executive office that the company said would allow it to be more responsive to its government customers. He has been president and COO since January 2010 and has previously led Lockheed’s electronic systems business and served as chief financial officer.

Marillyn A. Hewson, 58, who heads the company’s electronic systems business, will succeed Kubasik as president and chief operating officer, the company said.

Like other contractors, Lockheed Martin, the world’s largest defense contractor, has been making changes in recent years to adapt to slowing government spending. The company has announced layoffs at some of its business units and offered buyouts for employees at its corporate headquarters and internal business services organization. It has also consolidated some facilities to reduce overhead costs. As COO, Kubasik was one of the drivers of the company’s cost-cutting initiatives.

Still, the company posted strong returns for its most recent quarter. Lockheed said Thursday that its first-quarter profit reached $668 million ($2.03 per share), up from $530 million ($1.50) in the same period a year earlier. Sales jumped 6.3 percent to $11.3 billion.

Hewson has led Lockheed’s electronic systems unit since January 2010 and has been with Lockheed for 29 years.