Chinese clone Russia´s Su-27 fighter

China was for a long time the major buyer of Russian weapon systems, but times have changed, reports the Wall Street Journal:

ZHUHAI, China—A year after the collapse of the Soviet Union, a cash-strapped Kremlin began selling China a chunk of its vast military arsenal, including the pride of the Russian air force, the Sukhoi-27 fighter jet.
For the next 15 years, Russia was China's biggest arms supplier, providing $20 billion to $30 billion of fighters, destroyers, submarines, tanks and missiles. It even sold Beijing a license to make the Su-27 fighter jet—with imported Russian parts.

Today, Russia's military bonanza is over, and China's is just beginning.
After decades of importing and reverse-engineering Russian arms, China has reached a tipping point: It now can produce many of its own advanced weapons—including high-tech fighter jets like the Su-27—and is on the verge of building an aircraft carrier.
Not only have Chinese engineers cloned the prized Su-27's avionics and radar but they are fitting it with the last piece in the technological puzzle, a Chinese jet engine.
In the past two years, Beijing hasn't placed a major order from Moscow..

PS
Many western companies, including major ones, seem to be unbelievably credulous in their dealings with the Chinese. Sooner or later they will regret it. The Chinese are also extremely active in the area of industrial espionage - as are the Russians.