China's leaders regularly tout their fighter jets as symbols of military capability. But China's fighter jets have long had a major shortcoming: a lack of quality engines. China's defence industry has struggled with that flaw, but Beijing is working hard to fix it. Of all the fighters in China's arsenal, none are as important as the J-20.

The fifth-generation fighter also known as the "Mighty Dragon" is more than just a stealth fighter. It's an example that China, like the US, can build some of the best military technology in the world. It has become a symbol for the Chinese Communist Party, shown proudly at military parades and mentioned repeatedly in Chinese defence publications.

After a brutal brawl with Indian troops on their disputed border last year, China sent two J-20s to airbases in Xinjiang.

That deployment was too small to be of any real strategic significance, but the fact that China deployed its best fighter jet to a remote area in the Himalayas showed its seriousness. The J-20's deployment to China's Eastern Theatre Command is meant to send a similar message to Taiwan, Japan, and the US.

But the J-20, like all Chinese aircraft, has been hobbled by a lack of efficient and durable, high-performance jet engines.

That problem has plagued China's defence industry for a long time, and it's one Beijing is working hard to fix.

A Longstanding Problem

China's difficulties with jet engines may be surprising given the country's massive and successful military build-up. It's also no secret that China is skilled at reverse-engineering foreign technology to make domestic copies. Virtually every Chinese fighter jet is based on stolen or reverse-engineered designs.

There is precedent for reverse-engineering jet engines, but while China has plenty of access to Russian jet engines, Beijing's attempts to produce its own domestic designs have been largely unsuccessful.

One of its earliest versions of a domestically designed engine, the WS-10A, regularly broke down after just 30 hours of use.

There are many reasons for these failures. First, Russia is aware China has stolen its intellectual property before and is reluctant to sell Beijing its best engines. Moscow also doesn't sell standalone engines, instead including them on existing jets, which makes copying them difficult.

Second, reverse-engineering skill don't easily translate into proficiency at developing new jet engines from scratch. That requires technological know-how that takes years of intensive learning to develop and generations to perfect.

The 'Apex' of Technological Manufacturing

Perhaps most important, manufacturing jet engines is just extremely complicated.

"There are a few technologies that are really at the apex of technological manufacturing," and jet engines are one of them, Timothy Heath, a senior international and defence researcher at the Rand Corporation think tank, told Insider.

"These high-end technologies are so difficult to master that very few countries succeed. Many have failed," Heath added.

The main difficulty lies in the metallurgy and machining. A single engine on a civilian Boeing 747 airliner, for example, has at least 40,000 parts. Temperatures in that engine can reach as high as 2,500 degrees Fahrenheit, and its fan blades can spin well over 3,000 times a minute during an hours-long flight.

Blueprints for such an engine can be copied, but the secrets to producing and shaping metal parts that can withstand those temperatures and spin at such tremendous RPM over thousands of hours - not to mention external factors like wind resistance and corrosion - without breaking aren't easy to find.

Another disadvantage for China is that the entities tasked with developing these complex machines are state-owned enterprises (SOEs).

Historically speaking, SOEs struggle with innovation and developing cutting-edge technology. The reliance on reverse-engineering shows that this is the case with China, though there are certainly exceptions. "They're better at just reverse-engineering simpler components and building simpler things," Heath said. "All this requires a level of expertise and competence that SOEs just often are not very good at. You have to recognize the limitations of the SOEs in China when it comes to innovation."

'Crucial Technology Cannot Be Bought'

China is more than aware of its engine problems.

Liu Daxiang, the deputy director of the science and technology committee at the state-owned Aviation Industry Corporation of China, last year called the development of domestic jet engines "a serious and urgent political task" and said China was facing an "unprecedented challenge."

"The established countries in aviation have become more strict with us when it comes to technology access," Liu said, adding that recent US efforts to restrict opportunities for Chinese telecommunications firm Huawei "tells us that crucial technology cannot be bought, even if you spend big."

In an attempt to get direct access to the secrets of jet manufacturing, Chinese state-owned aviation firm Skyrizon, which has been blacklisted by the US government, tried to acquire a controlling stake in Motor Sich, a Ukrainian company that is one of the largest producers of engines for helicopters, jets, and missiles.

But the Ukrainian government this year stopped the deal, likely because of pressure from the US.

Despite the setbacks, China has made some progress. Modern variants of the WS-10 have progressed enough that some Chinese jets are being fitted with them, including a number of J-20s.

Chinese sources have said that the WS-15, an engine designed specifically for the J-20, "may be finished within one or two years" and that once those engines are installed, the J-20 will be "on a par" with the US's fifth-generation F-22 Raptor.

Ballpoint Pens, Microchips, And Jet Engines

But many challenges remain. The complexity of the materials and metallurgy process, the costs of acquiring and maintaining the scientific and machining expertise, and the reluctance of other countries to assist China for fear of intellectual-property theft are but a few of them.

China faces a similar predicament in manufacturing high-end microchips and semiconductors. Despite hundreds of millions of dollars and major efforts by state-owned enterprises, China has not been able to create its own computer chips.

"It's just that some of these technologies are extremely difficult to do, and it doesn't matter how much money you throw at it - if you don't have the right combination of people, technologies, and skills, it's just not going to come together so easily" Heath said.

But China doesn't give up easily. In 2017, a Chinese state-owned firm announced plans to mass-produce ballpoint pen tips for the first time. China already made billions of pens, but only after a five-year, multimillion-dollar effort did it develop the technology to make tips for those pens domestically. "All these elements can be reached only through long-term investment and incremental development," a Chinese researcher said at the time.