The U.S. Air Force announced it has certified the Falcon 9 rocket of Elon Musk's Space Exploration Technologies for national security space missions. Deborah Lee James, secretary of the Air Force, said in a statement, 'This is a very important milestone for the Air Force and the Department of Defense. SpaceX's emergence as a viable commercial launch provider provides the opportunity to compete launch services for the first time in almost a decade. Ultimately, leveraging of the commercial space market drives down cost to the American taxpayer and improves our military's resiliency.' Last year, Musk sued the Air Force, arguing his company should be able to compete against the United Launch Alliance, a joint venture between Boeing (BA) and Lockheed Martin (LMT). The lawsuit was eventually settled, with the Air Force vowing to work with SpaceX to get it certified to compete for contracts. The Air Force said it invested more than $60 million and 150 people in the certification effort.