It’s not obvious from the grainy photos of the J-20 what engines the plane currently uses, but it’s probably safe to assume they’re Russian AL-31Fs—still the best engines China reliably has access to. However, the AL-31F is clearly inadequate for the apparently heavy J-20. Even the up-rated 117S version of the AL-31F ‘would likely not be sufficient to extract the full performance potential of this advanced airframe,’ Kopp and Goon wrote. To perform at its best, the J-20 will probably need purpose-designed motors. And developing those could take a long, long time.

Equally vexing to Beijing’s aerospace designers and military planners are the sophisticated electronic, conceptual and human systems required in and around a modern fighter aircraft in order for that aircraft to deliver a useful military effect.

Richard Aboulafia, an analyst with the US Teal Group, told the Internet trade publication Defense Tech that a modern fighter requires at least 11 supporting systems to be effective, including but not limited to sound mission planning, a talented and disciplined pilot, good maintenance personnel on the ground, accurate weapons, an advanced radar and other electronic systems inside the aircraft plus ‘off-board’ radar detection provided by purpose-built command-and-control planes and the reliable ministration of an aerial tanker.

Of all the systems required by a modern fighter, Beijing has mastered just one, Aboulafia said—and that’s the airplane’s physical structure itself, minus the engines.

Still, according to Kopp and Goon the J-20 represents a profound shift in the Pacific balance of power. ‘Any notion that an F-35 Joint Strike Fighter or F/A-18E/F Super Hornet (flown by the U.S. Navy and Australia) will be capable of competing against this Chengdu design in air combat, let alone penetrate airspace defended by this fighter, would be simply absurd,’ they wrote.

And even the more cautious Ding says he can imagine a near-future where the J-20 dominates.