Su-35 Flanker: Why Russia Sell Its Best Fighter Jet to China?

Article Summary – China’s 2016 deal for 24 Russian Su-35s was never about fleet size; it was about technology.

-Beijing wanted the AL-117S engines, Irbis-E radar, and thrust-vectoring know-how it still struggled to master for its own J-20 and J-16 programs.

Su-35. Image Credit: Creative Commons.

Su-35 Fighter. Image Credit: Creative Commons.

-Russia, under post-Crimea sanctions, needed cash and saw a lucrative export; China saw a last chance to mine Russian design secrets before going fully domestic.

-The Su-35s filled a short-term capability gap over the South China Sea and Taiwan.

-Still, their real value was as flying laboratories that accelerated China’s engine, avionics, and EW development at Moscow’s long-term expense.

Russia Sold the Su-35 Flanker to China: Mistake?

In 2016, China received its first batch of Russian-made Sukhoi Su-35 Flanker D fighter jets.

This was part of a larger order of 24 total fighters, which were eventually delivered to the CCP.

At first glance, this made no sense for China, which already flew domestically made variants of the Su-27, so why would it bother purchasing other Russian aircraft?

The answer lies in its engines. The Su-35 uses more advanced engines than its predecessors and includes thrust-vectoring nozzles for enhanced maneuverability.

For China, which has struggled to produce high-performance engines domestically, the Su-35 was a significant prize.

In the long term, the deal was China’s last step toward reducing its reliance on Russian- and Soviet-made parts and allowed it to finally get its hands on good engines finally.

A Brief History of Sino-Soviet Trade

The history of Sino-Soviet trade goes back to the early Cold War. With both China and the USSR being communist powers, the two naturally found much common ground and engaged in trade.

China gained Soviet military technology, such as tanks and aircraft, while Russia gained minerals and other goods for its economy. During the Sino-Soviet split in the 1960s, trade essentially halted between the two, and China began its strategy of reverse engineering Soviet technology (a lot of details are being omitted for time’s sake).

However, as China’s industry was still maturing, it was unable to fully replicate the advanced components like avionics and engines (at the time ,the USSR was a leader in those industries next to the U.S.).

Su-35. Image Credit: Creative Commons.

Su-35. Image Credit: Creative Commons.

Even after the Cold War, when China was in the midst of its economic boom,it  still faced significant challenges in producing reliable, high-performance engines for its next-generation fighters.

This became a significant issue in the 2000s when the CCP began work on its first fifth-generation fighter.

The WS-15 engine, intended for the J-20 stealth fighter, was still under development and plagued by delays.

The Su-35’s AL-117S turbofan engines were a significant technological advantage, offering supercruise capability and thrust-vectoring features that China had not yet mastered.

Russia refused to sell these engines separately, which forced China to buy the entire aircraft package. For Beijing, the engines were the crown jewel of the deal, providing an opportunity to study and potentially reverse-engineer them to accelerate domestic engine programs.

Why China Wanted the Su-35

The Su-35 featured advanced avionics and radar systems superior to those in China’s existing fourth-generation fighters.

The Irbis-E radar, for example, provided exceptional detection range and multi-target tracking capabilities, serving as a benchmark for China’s own radar development.

The aircraft also featured thrust-vectoring nozzles, granting superior maneuverability in close combat, a capability China sought to replicate in its future designs. These technologies were not just operational assets; they were learning tools for China’s engineers and defense industry.

For China, the Su-35 served as a brief stopgap measure during a period of rapid modernization within the PLAAF. In 2015, China still operated a large fleet of older aircraft, including derivatives of the MiG-21 and Su-27.

While fifth-generation fighters like the J-20 were in development, they were not yet available in sufficient numbers to replace legacy platforms.

The Su-35, classified as a “4++ generation” fighter, provided an interim solution that could counter regional threats such as Japan’s F-15s and even challenge U.S. assets like the F-22 in specific scenarios.

Although China never intended to buy Su-35s in large quantities, the 24 aircraft strengthened its air superiority in sensitive theaters such as the South China Sea and Taiwan Strait.

Why Russia Agreed to the Deal

The deal was also beneficial for Russia, which needed some cash.

Following Western sanctions on Russia after the annexation of Crimea, Moscow sought to expand arms sales to China to offset economic losses.

For Beijing, the deal reinforced political ties with Russia and ensured continued access to advanced military technologies at a time when Western suppliers were off-limits.

The transaction benefited Russia’s defense industry while giving China leverage for future technology transfers. This deepening of Sino-Russian defense cooperation was as much about strategic alignment as it was about hardware.

China’s approach to the Su-35 deal was consistent with its long-standing strategy of acquiring foreign systems and reverse-engineering them to accelerate domestic innovation.

Analysts widely believe that China’s primary interest was not in operating the aircraft long-term but in absorbing its technology, especially engines, radar, and electronic warfare suites, for integration into indigenous platforms like the J-20 and J-16.

This pattern had precedent: China previously reverse-engineered the Su-27 to produce the J-11, a move that had already raised concerns in Russia about intellectual property and technology leakage.

Su-27 Flanker from U.S. Air Force Museum. Image Credit: National Security Journal.

A Practical Choice for Long-Term Gain

While the Su-35s were deployed to PLAAF units, their operational role was limited. They served more as testbeds and training platforms than as frontline fighters.

However, their presence carried symbolic weight, signaling China’s growing airpower and its ability to field advanced fighters comparable to Western fourth-generation-plus aircraft.

The acquisition also allowed China to evaluate Russian design philosophies and compare them against its own, providing insights into areas where domestic fighters needed improvement.

For China, it accelerated the development of the WS-15 engine and advanced avionics, contributing to the maturation of the J-20 program.

For Russia, while the deal was economically beneficial in the short term, it risked enabling China to erode Russia’s competitive advantage in fighter technology.

This concern has made Moscow more cautious about future high-tech transfers. For regional security, the acquisition temporarily enhanced China’s airpower, influencing the balance of power in East Asia and complicating U.S. and allied planning in the Indo-Pacific.

About the Author: Isaac Seitz

Isaac Seitz, a Defense Columnist, graduated from Patrick Henry College’s Strategic Intelligence and National Security program. He has also studied Russian at Middlebury Language Schools and has worked as an intelligence Analyst in the private sector.

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