Col. Hans Ritschard, 90th Medical Group commander, passes the guidon to Lt. Col. Timothy Christison, 90th Medical Support Squadron commander, during the 90th MDSS change of command ceremony June 5, 2015, at F.E. Warren Air Force Base, Wyo. The ceremony signified the transition of command from Lt. Col. David Brown to Christison. (U.S. Air Force photo by Airman 1st Class Malcolm Mayfield)