China's domestically developed S4000 Stratosphere Airborne Wind Energy System (SAWES) successfully completed a test flight in Yueyang City, central China's Hunan Province, on Friday, marking its first flight test in an urban setting.

The world's first of its kind, the S4000 is designed to operate at altitudes of up to 4,000 meters and has a design life of up to 20 years.