AEROSPACE

McDonnell Douglas President to Retire: The St. Louis-based aerospace company said its president and chief operating officer, Gerald A. Johnston, will retire at the end of the year due to health problems. Johnston, 62, had returned to work at McDonnell Douglas Corp. in October, 1992, after a yearlong bout with pancreatitis. Although he’s feeling better, Johnston told the board of directors he no longer had the energy or stamina to “consistently give the company the 150% that I was used to.� No successor was named. Johnston has spent 38 years at McDonnell Douglas, beginning in 1956 as an associate engineer in guidance and control for Douglas Aircraft Co.’s fledgling missile and space division.