Developing a stealth fighter-intercept plane hasn't been any easier or cheaper for China than it was for the U.S. "The technical barriers and development costs for such aircraft are enormous and the U.S. has struggled for years to deliver on their potential," the A.P. explains, adding that China faces the additional hurdle of developing a capable engine. Here's a still from the video:
Analyst David Axe, writing at Wired's Danger Room, calls the flight "a huge leap forward for China’s ambitious stealth warplane program." But, he added, "there are still more questions than answers about China’s second stealth fighter model."
It's worth keeping a bit of perspective on China's developing high-tech military capability. Because China can't produce its own jet fighter engines, it's buying them from Russia. The U.S. doesn't seem to consider Russia's air force to be a particularly scary national security threat. At least on this one limited but important metric, China's military capability is still behind Russia's.