This might look like a B movie script, but imho what we are seeing in our skies have been here all along. They belong to the civilizations that created the pyramids, call them Atlanteans, Hyperboreans, but they are proof that advanced civilizations existed in our planet and still do.
These machines are even mentioned in Hindu texts, Vimanas. Where are they located? Underwater bases (Atlantis anyone) and Antarctica. The Germans knew of this and wanted to make contact with these ancestors, and i think they did, that's why they went to Antartica and had a base there.
World powers tried to defy these ancestors in 1946 with Operation Highjump and were totally defeated. These things, these ancestors, come from our own planet (underwater bases / inner earth) and not from another dimension or another planet, somehow they can defy G forces, maybe the pilots of these things are robotic in nature or found a way to overcome the gravitational forces that is unknown to us.
i don't buy anything that comes from the To The Stars Academy or the Pentagon, they are lying to you. They absolutely know who pilots these ships and who owns this technology, these are the same that kicked their asses in 1946.