The makers of China's new J-20 stealth fighter revealed the combat mission of the aircraft, and one of its key tasks would most likely see it getting shot down by decades-old US and European fighter jets.

The J-20 has an impressive stealth design and good missiles that make it ideal for attacking some key targets that could degrade or even cripple the US military.

But when it comes to old-fashioned air superiority, which China says the J-20 will take on, the US's F-15 and Europe's Typhoon could most likely beat it with ease.

The US's top air-superiority fighter, the F-22, outclasses the J-20 by a wide margin in terms of taking control of the skies.

The makers of China's new J-20 stealth fighter revealed the combat mission of the aircraft, and one of its key tasks would most likely see it getting shot down by decades-old US and European fighter jets.

The J-20 has impressed observers with its advanced design and formidable weapons, but the jet's actual combat mission has remained somewhat of a mystery.

Read more: The real purpose behind China's mysterious J-20 stealth fighter jet

But Andreas Rupprecht, a German researcher focused on China's air power, recently posted an informational brochure from the Aviation Industry Corporation of China, the J-20's maker, laying out its mission.

It described the J-20 as a "heavy stealth" fighter that's "renowned" for its dominance in medium- and long-range air combat and first lists "seizing & maintaining air superiority" as its core missions.

It also lists interception and deep strike as missions for the J-20, falling roughly in line with Western analyses of the jet's capabilities.

But the J-20s purported air-superiority role is likely to raise more eyebrows.

Read more: China's most advanced stealth fighter may now be able to strike targets at greater distances than ever

J-20 loses the old-fashioned fight for the skies

Two J-20 stealth fighter jets perform during the 12th China International Aviation and Aerospace Exhibition, also known as Airshow China, in November. AP Photo/Kin Cheung

Justin Bronk, an aerial-combat expert at the Royal United Services Institute, told Business Insider that for the J-20, fighting US or European jets for control of the skies represents a losing battle.

The J-20 is "certainly likely to be more capable as an air-superiority platform than anything else the People's Liberation Army Air Force" — China's air force's official name — "is currently operating," Bronk said.

"With a powerful radar and multiple internal air-to-air missiles as well as long range, it certainly shouldn't be dismissed as an air-superiority machine," he continued.

But just because it's China's best doesn't mean it can hold a candle to Europe's Typhoon fighter or even the US's F-15, which first flew in 1972.

"In terms of thrust to weight, maneuverability, and high-altitude performance, it is unlikely to match up to the US or European air-superiority fighters," Bronk said.

China's J-20 made a solid entry into the world of stealth fighter aircraft and became the only non-US stealth jet in the world. It's designed to significantly limit the ability of US radar to spot and track the large fighter, but the stealth mainly works on the front end, while the J-20 is flying straight toward the radar.

Tactically, experts have told Business Insider, the J-20 poses a serious threat in the interception and maritime-strike roles with its stealth design, but so far the jet has yet to deliver.

Read more: China appears to have rushed its J-20 stealth fighter into service with an 'embarrassing' flaw

China has suffered embarrassing setbacks in domestically building jet engines that would give the J-20 true fifth-generation performance on par with the F-35 or the F-22.

Bronk said China still appears years away from crossing this important threshold that would increase the range and performance of the jets.

"The engines are a significant limiting factor" in that they require inefficient use of afterburners and limit high-altitude performance, Bronk said.

What air superiority looks like

An F-15C Eagle preparing to refuel with a KC-135R Stratotanker. US Air Force Photo

As it stands, the J-20 couldn't match the F-15 or the Eurofighter Typhoon, or even get close to an F-22, Bronk said.

"Against the F-15C and Typhoon, the J-20 has a lower radar cross section but worse performance, and its air-to-air missiles are unlikely to yet match the latest [US] series and certainly not the new European Meteor," Bronk said.

Bronk said that China had made great strides in air-to-air missile development and was testing at an "extremely high" pace, so the capability gap could close in a few short years.

But how does the J-20 stack up to the greatest air-superiority plane on the planet today, the F-22?

Read more: How China's stealthy new J-20 fighter jet compares to the US's F-22 and F-35

"The F-22 likely significantly outperforms the J-20 in almost every aspect of combat capability except for combat radius," Bronk said, referring to the farthest distance a loaded plane can travel without refueling.

Undoubtedly, the J-20 represents a significant leap in Chinese might and poses a serious and potentially critical threat to US air power in its ability to intercept and launch deep strikes.

But in the narrow role of air superiority — beating the best fighters the other side can offer to gain control of the sky — the US and Europe could most likely beat down China's J-20 without much trouble.