The evidence suggests this thing is 100-1000+ years more advanced technologically then our own military.

The notion 'it's a covert unawcknolodged black ops top secret project made by our/some government' is fine, I'd be okay with it being the new SR-71.

But that doesnt solve one very significant problem, where the hell did the source technology come from to build it. Either way no matter the significance of its origin or who actually owns it, everything points to a singularity of it not being human based technology to begin with regardless of ownership. You cant fake technological progress like this, their is no shortcut for time.

If this is ours (human), it's been in development for a minimum of 50+ years. Where we were 50+ years ago as a species does not match with what would be required technologically to begin building or understanding this. It would have been game over, every world power would have collapsed under the supremacy of this technology instantly. The fact it had to be kept under wraps is a crime against humanity and scientific progress that translates into trillions of dollars of damages, +millions of lives, and pre meditated global climate destruction. This thing could create world peace, unprecedented economic/technological growth, interstellar habitation, reduce poverty to zero. Are you really okay with this being a weapon for the most powerful military on the planet? Is this the great filter? I'm serious.

TLDR;

Option 1: We found something, back engineered it.

Option 2: Non human lifeforms.

Option 3: Genius level sauvaughnt inventor with billions+ in funding created something, without anyone noticing, using a new version of physics he created that will change the world forever and has global supremacy over all military powers combined with that one vehicle.

Option 4: Swamp gas from a weather balloon was trapped in a thermal pocket and reflected the light from Venus.

If you have other options or ideas on its origin let it be known, regardless one thing is certain, this will change everything. We are witnessing history.

The laws of physics never change but our laws of understanding always will.