U.S. Air Force Staff Sgt. Sherita Tisdom, Air Force Life Cycle Management Center medical system functional analyst, and Senior Airman Jeremy Karcher, 779th Aerospace Medicine Squadron bioenvironmental engineer, sing together during the 2015 Tops in Blue World Tour Aug. 28, 2015, at the Abilene Civic Center in Abilene, Texas. Tops in Blue is composed of all active duty Airmen who come from a wide variety of Air Force career fields. (U.S. Air Force photo by Senior Airman Kedesha Pennant/Released)