The aerospace and defense industry is an ever-evolving landscape of large and small companies jockeying to add value to their customers and upend their competitors. Mergers and acquisitions have been a formidable tool in shaping the industry. A handful of leaders stands out for their adept use of mergers, acquisitions, divestitures and spinoffs. They are ranked here alphabetically. Dollar amounts are in then-year figures and not adjusted for inflation.