SpaceX will launch falcon 9 with 15 spare satellites which will include the OneWeb First Generation and a single prototype of the OneWeb Second Generation. Boosters are expecting to return to the Landing Zone 4 in California at the Vandenberg Space Force Base. The Countdown was aborted at T-55 second mark on May 19th at 9 AM with backup launch opportunity activated for Saturday May 20 at the time of 9:15 AM ET.