The Chinese People's Liberation Army (PLA) started a series of exercises in the South China Sea on Thursday, as Chinese netizens commemorated the death of a heroic PLA pilot whose plane collided with a US spy aircraft conducting close-in reconnaissance on China 20 years ago.

China has become much stronger than it was when the incident happened, as it has many advanced weapons and equipment now in service, analysts said, noting that as the US continues to intensify close-in reconnaissance operations on China, the risk of another similar incident is rising.

Military exercises will be held in a circular zone with a radius of five kilometres in the South China Sea, west of the Leizhou Peninsula, from Thursday to the end of April. The entry of other vessels is prohibited, reads a navigation restriction notice released by China's Maritime Safety Administration on its website on Wednesday.

Thursday is also the 20th anniversary of the Hainan Island incident that occurred on April 1, 2001, when PLA Navy pilot Wang Wei's J-8II fighter jet collided with a US EP-3 signals intelligence aircraft above China's exclusive economic zone southeast of Hainan Island. The US aircraft was conducting close-in reconnaissance in the South China Sea.

Remembering the incident, the South China Sea Strategic Situation Probing Initiative (SCSPI), a think tank based in Beijing, released an article on Thursday pointing out that the US military's aerial close-in reconnaissance on China has been on the rise over the past 20 years and the risk of another similar incident is also rising.

On March 22, a US Air Force RC-135U reconnaissance aircraft edged near South China's coastal regions and was only 25.3 nautical miles away from China's territorial sea baseline; and on August 25 last year, a US Air Force U-2 high-altitude reconnaissance aircraft trespassed into a no-fly zone of a PLA live-fire exercise, the SCSPI article said, stressing the risks.

Unlike 20 years ago, the PLA now operates many advanced weapons and equipment, including the J-20 stealth fighter jet and two aircraft carriers. And with them, today's PLA troops are continuing Wang's work in safeguarding China's security, Chinese netizens said on social media.

The PLA exercise in the South China Sea throughout April is likely a regular one, as the same sea region also hosted a month-long exercise in March, indicating the region is a frequently used exercise range, a Chinese military expert told the Global Times on Thursday, requesting anonymity.

Every PLA exercise leads to better combat preparedness, and the drills in the South China Sea are also warnings to the US and other countries that have ill intentions against China, the expert said.

The PLA will be prepared to deal with any hostile activity, and if another incident like the one that happened 20 years ago is to happen again, it will be the US that will have to be responsible for it, the expert said.

It has become a consensus between the Chinese and US militaries that crisis management must be enhanced so that uncontrollable military conflicts can be avoided, the SCSPI article said, noting that the two sides should further discuss and form operable norms over close-in reconnaissance.

"The current China-US relations, as well as the world today, cannot afford to see another warplane collision-like incident," the article reads.