Boeing's defense business has taken on greater importance as the company struggles with commercial airplane production. More than 3,200 Boeing (BA 0.08%) workers at the company's St. Louis-area defense factories went on strike Monday after the International Association of Machinists and Aerospace Workers (the IAM Union) rejected a modified contract offer from the company. The IAM Union members help build and maintain military aircraft and defense systems, including the F-15EX fighter jet and the MQ-25 Sting ...