AEROSPACE

Martin Marietta President to Retire: The Bethesda, Md.-based defense company said its president and chief operating officer, A. Thomas Young, will retire next July 1. Young said in a statement that the move is consistent with the company’s practice of a well-planned transition. Martin Marietta Corp. said it will identify a successor “at the appropriate time.” Young joined the company as vice president of research and engineering for aerospace in 1982 and became president in 1990.