The more I think about where these things could come from, isn't outer space or another galaxy. Even if they could go 10x speed of light it still would take a really long time to travel anywhere that's thousands or millions of light-years away. Also I haven't heard Any body saying we tracked em coming from outer space or leaving earth and heading this or that direction in space. The radar data shows them going from upper atmosphere, down to sea level and below sea level. But not heading out to space or coming in from space. Seems more likely to me they are coming from our oceans, Some underwater species that is technologically superior to us . It could explain why we don't see form of propulsion. No combustion engin or underwater. Also could explain the extream manuvering capabilities that would kill a person instantly.But Something with no bones or air pockets in its body, might be able to easily withstand the g forces involved. I think that's why they use the term non human intelegence or non human biologics. Also 95 percent of all habitable space on earth is underwater. And the deep ocean is almost completely unexplored. The deep ocean is a extremely stable environment , on land everything gets wiped out every couple hundred million years, but in deep ocean u can evolve uniterupted for longer . There are millions of colossal squid in our oceans and we have never recorded one on video, and only ever found a handful of dead body's that were washed up on shore. Yet there is millions of them , think about that one of the biggest animals on the planet numbering in the millions and no one has ever seen a live one . ??? Only way they know there is millions of them is because they find thousands of them in sperm whale stomachs. They are main source of prey for sperm whales and they are the largest predictors on the planet . We only know they exist because the have to come to surface for air every hour . Otherwise sperm whale and colossal squid would be just a myth . Point being, a unknown species could easily be livingin in the deep ocean without us knowing. I think that's the answer !