The picture shows aircraft carrier Shandong berths at a naval port in Sanya. China's first domestically-made aircraft carrier Shandong (Hull 17) was officially commissioned to the PLA Navy at a military port in Sanya, South China's Hainan Province, on the afternoon of December 17, 2019, making China one of the few countries in the world that have multiple carriers. Chinese President Xi Jinping attended the commissioning ceremony for the new aircraft carrier, which was named after China's eastern province of Shandong, and handed military flag to Senior Captain Lai Yijun, commander of the ship. Photo:China Military

China's second aircraft carrier, the Shandong, reportedly wrapped up its third voyage of this year, and returned to the Dalian Shipyard in Northeast China's Liaoning Province on Sunday.

It conducted frequent fight jet takeoff and landing training, and commercial satellite imagery indicates it might have conducted joint exercises with a submarine, media reports said on Monday.

The domestically built aircraft carrier sailed back to the Dalian Shipyard on Sunday after training at sea for 23 days, Hong Kong-based news website wenweipo.com reported on Monday.

On November 21, the Shandong left the shipyard and sailed toward the Yellow Sea for exercises there, after which it headed north on December 6 to the Bohai Sea for more exercises, the report said, citing two navigation restriction notices released by the Maritime Safety Administration of Liaoning Province.

For several days, J-15 fighter jets frequently took off and landed on the Shandong as the aircraft carrier completed training exercises, including maximum sorties and recovery, China Central Television (CCTV) reported on Monday.

Fighter jets are the core combat forces of an aircraft carrier, and integrating fighter jets and the carrier to their highest potential is a key part of forming combat capability, a military expert told the Global Times on Monday on the condition of anonymity.

During its exercises in the Bohai Sea, the Shandong was caught on foreign commercial satellite images sailing at a high speed, and what seems to be a submarine was also spotted near the aircraft carrier, possibly conducting joint exercises, the wenweipo.com report speculated.

In actual combat, an aircraft carrier will not operate alone, but in a combat group consisting of other warships like cruisers, destroyers, frigates, replenishment ships and attack submarines, analysts said.

If the submarine was related to the Shandong and was part of a joint training session as media reports speculated, it could mean another step for the aircraft carrier to form combat capability, the expert said.

This was the third time the aircraft carrier has set out for missions in 2020. The first was reportedly held in the Yellow Sea and Bohai Sea from May 25 to June 17, and the second took place in the Bohai Sea from September 1 to 22. This means the Shandong was out at sea for exercises for nearly 70 days in 2020, wenweipo.com reported.

It has been almost a year since the Shandong entered service with the Chinese People's Liberation Army (PLA) Navy at a naval base in Sanya, South China's Hainan Province on December 17, 2019.

Chinese military observers have been eagerly waiting to see the Shandong eventually return to Sanya, the doorstep of the South China Sea, and act as an effective deterrent to stabilize the regional situation, in which the US has continuously conducted provocative activities such as sending reconnaissance planes and conducting military exercises in the area.

With the Shandong beginning to form combat capabilities, the PLA's dual aircraft carrier strike group is no longer just a concept, analysts said.