China's first domestically built aircraft carrier, the Type 001A, has reportedly begun its fourth sea trial on Thursday ahead of its anticipated April 2019 commissioning, the Global Times reported. The vessel is expected to test its aviation systems, helicopters, and fighter jets.

The trial began after months of maintenance and upgrades on the Type 001A, a 315 meter (1,033 feet) long, 50,000-ton vessel, at its homeport of Dalian in Liaoning province.

Recent social media photos and videos showed three jet blast deflectors and three aircraft on the flight deck. The deflector is a safety device that redirects high energy exhaust from a jet engine to prevent damage and injury, indicating that the trial could involve takeoff and landing drills.

While no official announcement of the tests has been made, a Thursday statement by the Maritime Safety Administration of China said that a region of the east coast of Dalian in the northern Yellow Sea would be closed to regular marine ­traffic between Wednesday and Sunday for military exercises.

"During this sea trial, the carrier's aviation division will be coordinated for the first time," Wang Yunfei, a naval expert and retired PLA Navy officer, told the Global Times Thursday. He said the vessel would also be testing its radar, communication, air traffic control systems, along with its takeoff and landing equipment.

Wei Dongxu, a Beijing-based military analyst, told the Global Times that there would also be a test of the vessel's systems including power, damage control, weapons, and navigation systems.

Yunfei believes the J-15 fighter jets and helicopters will fly around the carrier to test and coordinate systems related to takeoff and landing. "If everything works well, a takeoff and landing test is possible," Yunfei noted.

Dongxu said that J-15 pilots have already trained for takeoff and landing on the Liaoning, China's first aircraft carrier. He noted that full-sized models of the aircraft would also be used to test loading and maintenance equipment.

Chinese Ministry of National Defense spokesperson Wu Qian said at a monthly press conference on Thursday that the PLA Navy is planning celebration activities for the 70th anniversary of its founding.

Yunfei said the PLA Navy might hold a maritime parade in April as a part of the celebration, according to state media reports. There is also reason to believe the ceremony could be based around the commisioning of the Type 001A.

The aircraft carrier has already conducted three sea trials in May, August, and October respectively.

Soon, the US Navy will have to keep tabs on two Chinese aircraft carriers, something that could complicate their freedom of navigation patrols in the South China Sea, and an early warning that conflict on the open seas could be ahead.