A Bulgarian air force Aero L-39 Albatros taxis on the runway during exercise Thracian Viper 20, Sept. 23, 2020, at Graf Ignatievo Air Base, Bulgaria. Thracian Viper 20 is a multilateral training exercise with the Bulgarian air force, aimed to increase operational capacity, capability and interoperability with Bulgaria. The exercise provided an opportunity for U.S. Airmen to train with partners and NATO allies in order to improve interoperability and readiness. (U.S. Air Force photo by Airman 1st Class Ericka A. Woolever)