A J-20 stealth fighter jet attached to the Chinese People's Liberation Army Eastern Theater Command takes part in exercises. The aircraft is not equipped with a Luneburg lens, a radar reflector used to make a stealth aircraft visible to others in training or non-combat flights. Photo: Screenshot from China Central Television

 The J-20, the most advanced, stealth-capable fighter jet of the Chinese People's Liberation Army (PLA) Air Force, has entered the next level of combat readiness, analysts said on Monday, after the aircraft was spotted flying without a Luneburg lens, a small device used to intentionally expose a stealth aircraft to others in situations like training or non-combat flights.

At the Qingming Festival on Sunday, the traditional tomb-sweeping day, pilots of J-20 jets paid respect to the heroic Chinese pilots who fought in the Korean War (1950-53), China Central Television (CCTV) reported on Sunday.

The former unit of Sun Shenglu, a heroic Chinese pilot in the war, is now equipped with J-20 fighter jets, Sun Teng, a J-20 fighter jet pilot, said on CCTV.

Sun Shenglu was part of the Wang Hai Air Group, which is now affiliated with the PLA Eastern Theater Command, according to openly available information. The PLA Air Force announced in 2019 that the Wang Hai Air Group was equipped with the J-20.

"Air Force pilots in the new age will inherit the spirit of 'aerial bayonet fighting,' train to prepare for combat, be ready at all times for combat, and resolutely safeguard national sovereignty and dignity," Sun Teng said.

The CCTV footage also showed a J-20 making aerial maneuvers, and some frames showed that this J-20 was not equipped with a Luneburg lens. Further, the lines of the aircraft's side missile bay were different from previous J-20 fighters, a separate report by CCTV said on Monday,

A Luneburg lens is a small device used to expand the radar cross-section of an aircraft, which means it can make a stealth aircraft visible to radar, a Chinese military expert who asked to remain anonymous told the Global Times on Monday.

In regular training, friendly radar facilities need to track stealth aircraft to monitor their activities and assess training results. In other non-combat scenarios like transit flights, making the presence of stealth aircraft known to others can avoid accidents, the expert said, noting that in some military operations, there could also be a need for such planes to show themselves to achieve deterrence while also hiding their true stealth specifications.

In most previous reports on the J-20, the stealth aircraft shown carried this radar reflector under its belly, military affairs observers said.

By removing it, the J-20 will go stealth as it was designed to, and this means it is engaged in a real combat scenario-oriented mission, the expert said, noting that the J-20 has entered the next level of combat readiness.