China recently made history as the first country besides the US to field stealth aircraft with its J-20 fighter, but reports from its regional rival, India, indicate that it may want to go back to the drawing board.
The Indian Defense Research Wing says its Russian-made Su-30MKI fighter jets can spot the supposedly-stealth J-20s, and has already observed them in flight.
Indian Air Force Chief Marshal Birender Singh Dhanoa said the "Su-30 radar is good enough and can pick it (J-20) up from many kilometers away," according to Indian news website Zee News.
India has been basing its Su-30MKIs in the northern part of the country to counter China's deployments of J-20s, which struggle to take off in the high altitudes near Tibet, Zee News reported.
The Su-30MKI represents a new and effective Russian jet with an advanced array of radars that Justin Bronk, an air combat expert at the Royal United Services Institute told Business Insider could probably spot the J-20.
"It is entirely possible that the Su-30MKI can pick up track information on J-20 from quite long ranges," Bronk said. "But what I would expect is that those tracks may be fairly intermittent and dependent on what headings the J-20 is flying on relative to the Sukhoi trying to detect it."
An Indian Air Force Su-30MKI
Bronk explained that unlike the US's F-22 and F-35 stealth jets, the J-20 doesn't have all-aspect stealth. This means that from some angles, the J-20 isn't stealthy. A senior stealth scientist previously told Business Insider the J-20 is stealthiest from the front end.
If China was flying the J-20s in any direction besides towards India, the Su-30MKI radars could have been spotting the jets from their more vulnerable sides.
"Also, it is possible that the Chinese are flying the J-20 with radar reflectors attached to enlarge and conceal its true radar cross section during peacetime operations — just as the USAF routinely does with the F-22 and F-35," said Bronk.
For safety and training purposes, stealth aircraft often fly with markers that destroy their stealth during peacetime maneuvers.
If this is the case with the J-20s, then India may be in for an unpleasant surprise next time it tries to track the supposedly stealth jets.
This article originally appeared on Business Insider. Follow @BusinessInsider on Twitter.
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