The Shenyang J-11 (Chinese: 歼-11; NATO reporting name Flanker-B, -L) is a twin-engine jet fighter of the People's Republic of China whose airframe is derived from the Soviet-designed Sukhoi Su-27. It is manufactured by the Shenyang Aircraft Corporation (SAC). The aircraft is operated by the People's Liberation Army Air Force (PLAAF) and the People's Liberation Army Naval Air Force (PLANAF). Development Proposed J-11 In the 1970s, the PLAAF initiated a project to develop a replacement for its MiG-19s. The Shenyang Aircraft Factory proposal, designated J-11, was a new light fighter powered by the British Rolls-Royce Spey 512 engine, with better maneuverability than the MiG-19 and better climb rate than the MiG-21. The project was abandoned due to difficulties in obtaining the engines. Background: purchase of the Su-27 China is the first foreign operator of the Su-27 and the only country to acquire the fighter before the Fall of the Soviet Union. The deal, known as the '906 Project' in China, marked the leap in Chinese aviation capability in the 1990s. Discussion of the aircraft purchase began in 1988 when the Soviet Union offered China fourth-generation fighters like the MiG-29. However, the Chinese negotiator insisted on purchasing the Su-27, the most sophisticated fighter Soviets had at the time. The sales were approved in December 1990, with three fighters delivered to China before the disintegration of the Soviet Union in 1991. Russia completed the Su-27 order and later allowed China to assemble and manufacture the Su-27 domestically. The domestically built ones were designated as the "J-11". The earliest batch of Su-27s were stationed at Wuhu air base in the early 1990s. In the next two decades, 78 Flankers were delivered under three separate contracts by the Russian KnAAPO and IAPO plants. Delivery of the aircraft began in February 1991 and finished by September 2009. The first contract was for 20 Su-27SK and 4 Su-27UBK aircraft. In February 1991, an Su-27 performed a flight demonstration at Beijing's Nanyuan Airport. Chinese Su-27 pilots described its performance as "outstanding" in all aspects and flight envelopes. The official induction to service with the PLAAF occurred shortly thereafter. China found some of the delivered Su-27UBKs are "second-handed", consequently Russia delivered 2 more Su-27UBKs to China as a compensation. Differences in the payment method delayed the signing of the second, identical contract. For the first batch, 70% of the payment had been made in barter transactions with light