I think that is plausible, sufficiently so if we were to rank potential explanations, that makes more sense. I don't know what kid invented the first paper airplane and threw it, but I know someone in the past did it, which might explain some of the bird carvings being flight worthy... Yeah! People in the past were not idiots, as evidenced by some of the stone work exceeding our abilities to duplicate with today's technology. Yeah, I agree!

Now, couple that with Lee's sighting, and other sightings- is it possible to have both explanations on the table?