Marines with Marine Medium Tiltrotor Squadron 163 perform pre-flight checks on MV-22B Ospreys prior to a large-scale training flight aboard Marine Corps Air Station Miramar, California, April 10. This training operation marks the last time the commanding officer of VMM-163 will participate in a squadron-sized event before relinquishing command. - Marines with Marine Medium Tiltrotor Squadron 163 perform pre-flight checks on MV-22B Ospreys prior to a large-scale training flight aboard Marine Corps Air Station Miramar, California, April 10. This training operation marks the last time the commanding officer of VMM-163 will participate in a squadron-sized event before relinquishing command.