Both have the lack of 90-degree angles typical of stealth shaping, which is designed to reduce radar detection.

As China modernizes its military, the designs "show the willingness of China's aviation industry to experiment and innovate," said Euan Graham, a senior analyst at the Australian Strategic Policy Institute.

"Whatever the merits or demerits, it appears to be a highly original design," he said. "They deserve kudos for that, and should shake off any lingering complacency that the U.S. and its allies always set the pace."