A People's Liberation Army Air Force (PLAAF) Su-27 fighter crashed in Rongcheng, Shandong Province on Sunday, killing two pilots.

Initial photos showing the crashed aircraft began appearing on microblogs on Sunday afternoon. China Central Television later reported the pilots' deaths in a Weibo account.

Judging from the photos, the crashed aircraft is a double-seat Su-27UBK fighter. The missing cockpit canopy suggests the pilots had ejected. It was unclear why they did not survive.

China has acquired a total of 40 Su-27UBKs from Russia since 1992. The last batch of 28 aircraft was delivered to the PLAAF in 2000 to speed up the training of pilots, Daniel Tong, founder of the Chinese Military Aviation website, told the Global Times.

The introduction of the Su-27 series fighter gave the PLAAF for the first time an admirable capability both in beyond-visual-range air combat and dogfights, he said.

Due to the lack of advanced training, Su-27UBKs have been intensively used to train third-generation fighter pilots.

China began producing the Su-27 series in 1996 and has developed at least four versions fully using domestically made parts and sub-systems. The J-11BS double-seat fighter, which is already being delivered to the PLA, will eventually replace the Su-27UBK, said Tong.