The name history is genuinely confusing, and much of it is unofficial. FC-31 (“Fighter China”) was an export-oriented company designation for the original demonstrator. J-31 was a tentative label widely used by outside observers, but it was reportedly never confirmed as an official PLA designation. J-35 refers to the more mature operational programme; the carrier variant is the J-35, and the land-based air-force variant, publicly shown in 2024, is the J-35A. In short, the shifting names track the aircraft’s evolution from a private demonstrator toward a fielded military type — and some designation details are still not fully pinned down by independent analysts.

Engine maturity has long been viewed as a potential constraint on Chinese fighter programmes, and the J-35 is a case in point. The lineage most often reported runs from the Russian RD-93, to the domestic WS-13 family, toward a more capable WS-19 (“Huangshan”), with a WS-21 mentioned in some accounts as an interim step. Sources disagree over which engine flies on current aircraft, and whether it enables supercruise. None of this is officially confirmed by China, and independent analysts caution that leaked performance claims — positive or negative — are difficult to verify. Any specific thrust figure attached to the type should be read as an estimate.

The J-35 is routinely compared to the F-35, and some commentators allege design influence aided by cyber-espionage. Analysts urge caution: broadly similar stealth silhouettes recur across fifth-generation designs — the South Korean KF-21 and Indian AMCA share comparable layouts — because similar requirements tend to produce similar shapes. A clear configuration difference is that the J-35 is twin-engine while the F-35 is single-engine. Claims that the two aircraft are equivalent in stealth, sensors, software or networking, or that one is simply a copy of the other, are not supported by public evidence, and should be treated with caution in either direction.

There is no reliable public unit-cost or cost-per-flight-hour figure for the FC-31 / J-35. It is a Chinese state programme, not sold on an open market, and Beijing has disclosed neither procurement prices nor operating costs. Any dollar figure circulating online — whether for the aircraft or a reported export version — is speculative. The same caution applies to production numbers: some 2025–26 reports infer roughly 30 airframes built in under a year from apparent serial numbers, but those are estimates drawn from imagery, not official data.