Two advanced-type aircraft were spotted flying in the People's Republic of China on December 26th, in an event that is assumed to be an implied public presentation of indigenous new-generation fighters. The first aircraft was identified as the fighter-bomber known in the West as the JH-XX (the real name unknown), and the second is likely the "classic" fighter J-50.
Update: according to clarified data, the designation of the fighter is not J-36 but J-50. The article below was corrected accordingly.
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The reason for the unusual activity is quite simple: the celebrations of the state founder Mao Zedong. As part of festivities, the Chinese authorities decided to lift off the secrecy shroud from two of its cutting-edge projects at once. This is evidenced by the list of cities where these jets were seen, as well as the air escort. Besides, these projects are led by different manufacturers, making an unintentional coincidence unlikely.
BIG: China’s next-generation (6th-gen) fighter jet made its first flight today. pic.twitter.com/ZryCr2baGA— Clash Report (@clashreport) December 26, 2024
That also explains why the JH-XX was accompanied by a Chengdu J-20, made by Chengdu Aircraft Industry Group. The J-50, in turn, was followed by a J-16 from Shenyang Aircraft Corporation, known for its J-35 fifth-generation fighter. Accordingly, the new aircraft that suddenly appeared in the skies of China was promptly designated J-50 as the next number in line by many media outlets.
To start off, the JH-XX is a fairly large aircraft, judging by images available in open sources. It implements the tailless delta wing configuration, without vertical stabilizer or it's too small to notice or folds into the body. This is to reduce the profile's visibility on radars.

JH-XX is notably larger than its escort, the J-20, which is known to be around 20 meters long and 13 m in wingspan (65 x 43 feet). Though it's unclear if both flew at the same altitude, complicating a visual evaluation.

As for the J-50, the new fighter is notable for its lambda wing design which remains an exotic choice in the industry. The same design was, for example, at some point considered for Lockheed Martin's NGAS tanker aircraft or realized in Boeing's X-45 combat drone.

J-50 is apparently lighter than the JH-XX, as suggested by the ordinary 3-point landing gear with single wheels. Given that the whole concept revolved around the aircraft's inconspicuousness, the armament bays must be fitted inside the body.
Another aspect worth noting is the uncrewed capability. Unfortunately, photos from such a distance cannot answer if the J-50 could be a drone or optionally piloted. Even if at this point there is a cockpit, installing one specifically for tests isn't an uncommon practice. For instance, Northrop Grumman made a piloted variant of the Model 437 Vanguard loyal wingman for experimentation.

Lastly, let us remind you that the so-called sixth generation of fighters is an exclusively provisional concept. Different countries have different visions of how it should like and what it should be capable of. But in general, the key features believed to be crucial for a 6th-gen are: optionally piloted with artificial intelligence, advanced low visibility technologies, high flight efficiency at all speeds, integrated long-range weapons, and supporting loyal wingmen.
The appearance of two candidates at once for being true 6-th generation is a strong statement and challenge to the West with its financial, bureaucratic, and political issues slowing down their own developments.
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