Not sure why everyone is convinced these are interstellar travelers. There are many more plausible possibilities such as simply being a small group of humans with advanced tech. They could be fabled Atlantians. Could be a different race or sub-species. Seems if they have the technology to completely evade our most advanced fighters and come on and off radar at will, they could hide a base somewhere on this big planet. I know it sounds totally far fetched, but as crazy as that sounds it is much much much more likely than interstellar travel.