Fifteen J-20 stealth fighter jets soared past Beijing skies in formation during the Communist Party of China's (CPC) centenary celebrations on Thursday, marking the largest number of the country's most advanced warplane displayed to the general public in a single event, with analysts saying that the aircraft has started mass production and demonstrated capability to safeguard the country.

The J-20s, five in each of the three V-shaped formations, flew past Tiananmen Square as part of aerial performances to celebrate the 100th anniversary of the founding of the CPC.

This marks the largest number of J-20s among all of its aerial performances, including air shows and parades, observers said, noting that the previous record was five, at the National Day military parade on October 1, 2019, also in Beijing.

A total of 15 J-20s flying together is unprecedented and amazing to behold, Fu Qianshao, a Chinese military aviation expert, told the Global Times on Thursday.

It indicates that the J-20 is becoming technologically mature and has entered mass production, with more units beginning to commission the aircraft, Fu said.

There could be some additional J-20s that served as unused substitutes for the aerial performance, and there must also be more J-20s that did not participate the event, as they were needed in routine training and combat missions, Fu said. "From this, we can image that China now has a pretty large fleet of J-20s."

On June 18, the People's Liberation Army (PLA) Air Force announced that the Military Development Vanguard Air Group, a heroic ace force, is now equipped with J-20s, becoming the second heroic ace force to fly the aircraft, following the Wang Hai Air Group that commissioned J-20s in 2019.

With more advanced warplanes like the J-20, the PLA will be able to better safeguard the country, Fu said.

In 2020, the US military had more than 500 stealth warplanes including fighters and bombers, with countries like Japan, South Korea and Australia also acquiring US-developed F-35 fighters, while China only had about 40 stealth fighter jets, US media outlet Forbes said in a report in July 2020. These numbers are expected to have increased over the past year, analysts said.

China has not revealed the size of its stealth warplane fleet, but the PLA is expected to continue to receive delivery of J-20s and other advanced warplanes in the future in order to fulfill its duties facing complicated external situations, experts said.

Song Zhongping, a Chinese military expert and TV commentator, told the Global Times on Thursday that the aerial performance of the advanced warplanes represented the latest achievement of China's aviation industry.

The J-20 is expected to continue to evolve based on its current form, and its improved variants will become even more powerful, Song said.

Experts predicted that the J-20 will eventually get domestically developed engines that can provide more powerful thrust and are capable of thrust vector control, and the aircraft could spawn variants like a twin-seat version.

Li Gang, the pilot of the J-20's first flight, told Hong Kong-based Phoenix TV in April that the J-20 is expected to be equipped with engines with 2D thrust vectoring nozzles.

Depicted by computer-generated imagery, four twin-seat J-20 variations were seen flying in formation in a video released by state-owned Aviation Industry Corporation of China, the developer of the aircraft, in January, in celebration of the 10th anniversary of the original aircraft's maiden flight.