Boeing performs fatigue testing on the structural airframe of the 787 Dreamliner at the Everett, Wash., site. Fatigue testing involves placing the 787 test airframe into a test rig that simulates multiple lifecycles to test how the airplane responds over time. While the structural test program already has validated the strength of the airframe, fatigue testing looks at long-term, continued use. This is the natural progression of testing on a new airplane and part of the process to achieve U.S. Federal Aviation Administration certification.