Whether the objects depicted in these ancient Mayan glyphs are UFOs as we understand them or not is an open question, but they appear similar to the craft the George Adamski drew during his sightings in the early fifties. In addition, the enormous amount of UFO activity taking place to this day over Mexico suggests that they might well have been seeing the same phenomena.
If so, then this has been going on a lot longer than most UFO researchers would like to believe. Your Out There editor thinks that the phenomenon is, simply, part of life on Earth, perhaps ongoing monitoring by advanced beings for their own reasons, or perhaps something that remains beyond our understanding.
In any case, the video is well worth a look.