Master Sgt. Stephen Nelson, 435th Contingency Response Group contingency air traffic controller, instructs Bulgarian paratroopers on the correct way to use a standard U.S. parachute during a flying training deployment, July 17, 2013, in Plovdiv, Bulgaria. American and Bulgarian paratroopers exchanged parachutes for the opportunity to conduct a wing exchange at the end of Thracian Summer. (U.S. Air Force photo/Airman 1st Class Trevor Rhynes)