Two Greek Air Force helicopters perform during the air show at the Tanagra Air Base, north of Athens, Greece, on Sept. 21, 2019. Greece's largest air show, the Athens Flying Week (AFW) Tanagra International Air Show 2019, took off Saturday for its 8th consecutive year at Tanagra Air Base, about 70 kilometers northwest of Athens. (Xinhua/Marios Lolos)