Area ruling could be one depending of how much they can compensate on the top side for the wings. Cutting drag is a key for speed and range. History of the f-102 is a good example of that importance. F-102 was not able to go supersonic while with area ruling modifications, f-102a was a supersonic aircraft...What would be the aerodynamic justification for the groove (if it exists)?
Wild if it's true (please be true).The grooves could be very very shallow, so that they are only noticeable in certain light angles. Of course it could be two airplanes, and I'm reminded of the previous rumors of “teacups” and “teapots”
The number of images of J-36 is far below J20’s early days. J-50 photos are more than J35’s, but still no where close to J20 days.The images have not been close (or clear) enough to clearly identify any aircraft numbering, but I'm surprise by how much footage the world is getting from this one and the J-36. Complete opposite from the J-20s and J-35s developments.