(Editor's Note: This story has been updated to reflect that Lockheed CEO Marillyn Hewson expects IOC for the F-35A program will occur sometime between August and December and the aircraft provides about 20 percent of the company's sales.) The F-35 Joint Strike Fighter program provides about 20 percent of Lockheed Martin's sales today and is the company's "biggest growth engine," chief executive Marillyn Hewson said Wednesday in New York. Speaking at Sanford C. Bernstein's strategic decisions conference, Hewson stressed...