[R. Scott]

I wonder if that saucer wobbled and swung back and forth as it hovered. It amazes me that a culture that can build an interstellar ship can’t come up with a control system that will allow a stable hover.

[Quix]

YOU MIGHT find Paul Hill's

UNCONVENTIONAL FLYING OBJECTS: a scientific analysis

has some discussion of the reasons for such.

I haven't read much of the book--not my science.

But from other docs, supposedly it has to do with surfing a gravity wave.

[HitmanLV]

Reminds me of a line from 'The Jetsons - "We've conquered space but haven't beaten the common cold!"