One reason for this difference, according to some Chinese sources, is that Shenyang's fighter may not be a fully air force-funded program, but an initiative derived from its losing competitor to the Chengdu J-20. The various plants of the Avic group, such as Chengdu Aircraft and Shenyang Aircraft, have a long tradition of rivalry. To overcome that, the group began bundling them together from 2008 into specialist subsidiaries in which they were supposed to work together. But the defense ministry opposed tight integration of the defense subsidiary—including Chengdu and Shenyang—in order to maintain closer control and probably to retain and foster competition among them.

But it is also possible that Shenyang's fighter does have an official sponsor: the Chinese navy. Shenyang is the builder of the navy's first carrier-based fighter–the Sukhoi Su-33-derived J-15. The J-31 would be more adaptable to carrier operations than the bigger J-20—although it might still need enhancements such as a bigger wing, an improved high-lift and control system, and thrust vectoring. Finally, the J-31 could be a smaller, less costly complement to the J-20.