
One case I can mention is 'Operation Deep Freeze' which took place in 1969 I believe. Several soldiers aboard navy ships claimed to have seen a USO come out of the ice and move towards the sky at great speed.
Another claim is that USOs have the ability to transverse material objects with ease such as ice or water.
I believe that often UFO and USO are one and the same after all where was a better place to hide. If they seek minerals is the ocean bottom not filled with them?
I do believe New Brunswick back in the 60's had a large vessel that was seen by many slowly fall from the sky and settle into the harbor complete with some green foam. It was reported to have left on its own power at a later time.