We won't be seeing AYYliens. We will be seeing all the experimental air craft inspired tech that is about 80 years out of our conceptual grasp. The sightings will be revealed to have been secret operations that no state could claim, as it would show the extent of their technological exploration. These craft had to be orphaned or otherwise unclaimed as a national security measure for all nations working on this tech. Some of what people will see in the near future will look like alien shit, but we aren't abreast of the true progress that has been made by our military industrial complex.