Another day, another market-moving tweet from the future President of the United States. This time the target was defense contractor Lockheed Martin, and its F-35 Joint Strike Fighter program. In the tweet, President-elect Trump called the F-35 program and its cost, “out of control” and pledged to save billions of dollars in military and other spending once he takes office. Shares in Lockheed and other defense contractors promptly dropped. But fixing concerns with the F-35 program is no easy task.