The head of Boeing Co.’s 737 jetliner program and site manager for the Seattle-area factory where the popular narrow-body plane is manufactured will retire at the end of the year. Scott Campbell is stepping down after three decades at Boeing, a career that encompassed all of the company’s current commercial aircraft product lines. “Earlier this year Scott came to me expressing his desire to retire and spend more time with his family, and I asked him to stay on for a bit longer,” Kevin McAllister, who heads Boeing’s commercial airplane division, said in a memo to employees. […]