Regarding the discussion on the J-XD's first flight:
Unless either of the following two is correct:
1. China has an equivalent to Plant 42, where aircraft manufactures can assemble and fly their demonstrators/prototypes from (the YF-22 did so), which is separate from the companies' respective aircraft manufacturing plants; or
2. China has an equivalent to Area 51, and that both Chengdu and Shenyang ACs did like what Lockheed did with their A-12 back in the 1960s (i.e. ship the secretive aircraft by parts to Area 51, assemble the aircraft and have its first flight from there) -
Then the first flights of J-XD1 from Chengdu AC and J-XD2 from Shenyang AC (demonstrator or prototype) are absolutely certain.
Both Plant 42 (in Palmdale, California) and Area 51 (in the middle of the Nevada's sparsely-populated arid mountain ranges) isn't exactly bordering or surrounded by sprawling cities, and during the first flights of both the YF-22 and A-12 there weren't portable cameras in everybody's pockets back then.
It should also be noted that both the YF-22 and A-12 had their first flights as technology demonstrators/prototypes - And that both flights took place during the Cold War.
So any attempts at applying what the Americans did with their YF-22 and A-12 to what Chengdu and Shenyang ACs should be doing with regards to their J-XD1/2 should be avoided.