US Air Force To Study Upgraded Falcon 9, Delay GPS III Launch Written 23 May 2018

Bloomberg News reports that the US Air Force has delayed the launch of its “first Global Positioning System III satellite from this month to October at the earliest as it reviews” the Falcon 9 Block 5 rocket. In a statement, Air Force Space and Missile Systems Center explained that the planned launch “has slipped due to ongoing SpaceX qualification testing and final engineering reviews by both SpaceX and the Air Force of Falcon 9 design changes.” The service is “working closely” with SpaceX, and plans to issue a “Flight Worthiness Certification just prior to launch.” 
More Info (Bloomberg News)