The aircraft has been the subject of heated debate
in air power circles for many years as Chinese military bloggers leaked images of the various preproduction prototypes.
The main questions being asked now are how much of a threat does the J-20 pose to American dominance of the skies in the Asia-Pacific region, and how much of a shift does the aircraft represent in terms of China's military capabilities?
In terms of a direct comparison with the US Air Force's own stealth fighters -- the F-22 Raptor and F-35 Joint Strike Fighter -- the J-20 is undeniably less stealthy.
The forward-mounted canards, poorly shielded engines and underside vertical stabilizers all limit the amount that its radar cross section -- which determines how visible the aircraft is to a radar -- can be reduced.
China also has significantly less know-how in terms of radar-absorbent coatings compared with the United States. Most importantly, it is extremely unlikely that the J-20 is equipped with anything approaching the F-22's and F-35's sensor suite.
This is crucial because it is not only the fact that they are hard to detect on radar that makes the F-22 and F-35 so deadly, but also the unrivaled situational awareness that their sensor-fusion capabilities give to their pilots.
However, despite the fact that the J-20 almost certainly cannot match the radar-evading properties or situational-awareness capabilities of US-made stealth fighters, it does have several advantages over them.
First, due to its larger size it will carry significantly more internal fuel, so it will have a longer range and be less dependent on vulnerable aerial refueling tankers in the vast Asia-Pacific. It also has larger internal weapons bays than either the F-22 or F-35, so it will be able to carry larger, longer-range missiles or a greater load of standard air-to-air and air-to-ground munitions than either of the US designs.
Finally, the J-20 is almost certainly going to be produced in far larger numbers than the F-22 and potentially even the F-35 if Chinese defense spending continues on current trajectories in relation to the United States and its allies.
What advantage does this give China?
Essentially, the J-20 will give the Chinese air force a long-range, hard-to-detect strike and interdiction fighter that can threaten the air bases, carriers, airborne warning and control systems, and refueling aircraft that the United States and its allies rely on to project air power over the vast distances of the Asia-Pacific.
While it is not as hard to detect as the F-35 and certainly the F-22, it would still be a lethal and evasive threat hidden within a mass of conventional aircraft and missile tracks in any flashpoint scenario.
The J-20, once in full scale production and service, will represent a significantly greater and fundamentally different threat to the Russian Su-30/35 Flanker family derivatives that currently form the leading edge of Chinese air power.
For the United States, it represents a serious threat in certain operational scenarios such as a confrontation over Taiwan or the contested Senkaku Islands.
For less capable militaries in the region such as Japan, South Korea and Taiwan, the J-20 represents a game-changing capability shift on the horizon from their primary military threat -- the Chinese air force.