Two government contractors announced Wednesday that their chief executives would retire, becoming the latest to step down in a spate of contracting-industry departures.

General Dynamics, which is based in Falls Church, said Jay L. Johnson, the company’s chairman and chief executive, plans to retire at the end of the year, while Arlington-based CACI International announced that Paul M. Cofoni, president and chief executive, would retire Dec. 1.

Phebe N. Novakovic is set to succeed Johnson at General Dynamics after taking over as president and chief operating officer last month. The move will make her the highest-ranking woman in the defense industry.

Novakovic previously served as executive vice president of General Dynamics’ marine systems group.

Johnson joined General Dynamics’ board of directors in 2003, became president and chief executive in 2009, and was appointed chairman and chief executive in 2010.

Under Johnson, a former chief of naval operations, General Dynamics came up with a distinctively shaped hull for its line of Stryker vehicles, a design meant to better deflect the blasts of improvised explosives. The company said he also oversaw the final development of two new aircraft, both set to begin service this year, in General Dynamics’ business jet unit.

At CACI, Daniel D. Allen, now president of U.S. operations, will become president and chief executive, while John S. Mengucci, chief operating officer of U.S. operations, will advance to become chief operating officer and president of U.S. operations, the company said.

Cofoni, who has been with CACI since 2005, will as of July 1 become chief adviser to the executive chairman of the board to ensure a smooth transition, according to CACI.

Under Cofoni’s tenure, CACI has grown to nearly $3.6 billion in fiscal 2011 from $1.6 billion in revenue in 2005. The company credited him with reengineering CACI’s recruiting programs to particularly zero in on hiring veterans.

The leadership turnover comes as many others in the industry are making their own changes. On the same day that Novakovic takes over the reins of General Dynamics, Christopher E. Kubasik will become the new chief executive at neighboring competitor Lockheed Martin, based in Bethesda.

McLean-based Science Applications International Corp. and Falls Church-based Computer Sciences Corp. also have named new chief executives this year.

“The Obama years have been tough on the people who run defense companies because programs are being cut right and left and the terms of contracts are being tightened,” said Loren Thompson, a defense industry consultant. “Frankly, I think some of these executives are just worn out.”

Rick Whittington, an analyst at Drexel Hamilton, said new executives will have to take a different approach to their businesses than those of the past, as federal spending contracts.

“The strategies are going to have to be altered to accommodate different fiscal and national strategic priorities in this country,” he said. “I think a lot of the boards have to be evaluating which individual is the correct one at the helm.”