China's AG600 seaplane conducted its first sea-based test flight on Sunday morning, marking a new milestone in the program.

The AG600 prototype used for test flight, operated by four crew members, took off at 9:28 am from the Shanzihe Airport in Shandong province's Rizhao and landed at 10:14 am on a designated area on the Yellow Sea off the neighboring city of Qingdao after a 46-minute flight.

The amphibious aircraft sailed on waters and then took off at 10:18 am to fly back to Shanzihe Airport. It completed a number of testing assignments during the operation, said Aviation Industry Corp of China, the State-owned aviation conglomerate that designed and built the seaplane.

To prepare for the sea-based test flight, the project team has overcome many difficulties caused by the COVID-19 outbreak to make sure the program could proceed on schedule, the company said in a statement.

Before the Sunday flight, the AG600 prototype had made more than 170 preparatory flights that lasted over 300 hours.

Currently, there are two AG600 prototypes under testing – one is for flight tests and the other is for ground-based static tests. The company has plans of manufacturing four additional prototypes for testing, designers have said.

AG600 is China's second amphibious aircraft after the SH-5, which was developed in 1970s for military purposes and retired a long time ago.

China's AG600 seaplane conducted its first sea-based test flight on Sunday morning. [Photo provided to chinadaily.com.cn]

The amphibious plane is one of three large-size aircraft to emerge from the nation's ambitious effort to become a top-tier player in the global aviation sector, joining the Y-20 strategic transport plane－delivery of which began in July 2016 to the Chinese Air Force－and the C919 narrow-body jetliner, which is being flight-tested.

Development of the AG600 was approved by the central government in June 2009 and began in September that year. Tens of thousands of researchers and engineers from more than 160 domestic institutes, enterprises and universities took part in the AG600 program. Construction of the first prototype began in March 2014 and was completed in July 2016.

The seaplane made its maiden flight in December 2017 in Zhuhai in South China's Guangdong province, taking off and landing at an airport. Ten months later, it carried out the first water-based takeoff and landing on the Zhanghe Reservoir in Jingmen, Central China's Hubei province.

With a length of 37 meters and a wingspan of 38.8 meters, the AG600 is roughly the size of a Boeing 737. Powered by four domestically designed WJ-6 turboprop engines, it has a maximum takeoff weight of 53.5 metric tons. These specifications make it the world's biggest amphibious aircraft, surpassing Japan's ShinMaywa US-2 and Russia's Beriev Be-200.

The AG600 will mainly be tasked with performing aerial firefighting and maritime search and rescue. It also can be refitted to conduct marine environmental inspections and marine resource surveys, as well as personnel and supply transportation, according to AVIC.

The aircraft is designed for both ground- and water-based takeoffs and landings and has an operational range of more than 4,000 kilometers. It is capable of rescuing 50 people during a maritime search and rescue mission.

When assigned to fight forest fires, it can collect 12 tons of water from a lake or sea in 20 seconds and then use the water to douse blazes over an area of about 4,000 square meters, the company said.

China's AG600 seaplane conducted its first sea-based test flight on Sunday morning. [Photo provided to chinadaily.com.cn]