The AG600, codenamed Kunlong, slides on the water surface in Qingdao, east China's Shandong Province, on July 26, 2020. (Photo provided to Xinhua)

China's indigenously developed AG600 large amphibious aircraft succeeded in its maiden flight over sea on Sunday morning in Qingdao, east China's Shandong Province, its developer announced.

The aircraft took off from the sea off Qingdao at 10:18 a.m. and completed the test flight after flying for about 31 minutues, said state-owned plane-maker Aviation Industry Corporation of China (AVIC).

The AG600, codenamed Kunlong, undergoes a test flight in Qingdao, east China's Shandong Province, on July 26, 2020. (Photo provided to Xinhua)

The successful maiden flight from the sea is a major step forward in the development of this large amphibious aircraft following its maiden flight in 2017 and first takeoff from a water reservoir in 2018, said the AVIC.