Yes I believe they are US- Man Made.
Was it a "triangular" Shape.
I saw one in 1999. Im sure there are several versions by now.
Going by other eye-wittness reports, they seem to have this almost comical/obvious? manoeuvre of flying directly over people who are observing them,
almost as a Joke... In a "Ha Ha look at me, but no-one will believe you. etc etc". Fashion.
The one I saw, flew directly overhead, at night time, with no sound. Only a 100-200ft or so off the ground.
Im sure that they use infrared imaging, so they can obviously see people on the ground, and fly over as a lark.
It could be part of the Test flights for these craft, just to see if anyone reports it etc.
Most people dont.
I waved at mine, so I would think the "Pilot" was having a great laugh....in a serious way.
What is their purpose?.......No Idea.
Some people have stated they are lifting platforms, probably Intelligence gathering craft too, who knows if they are armed? Maybe not, maybe that is
why they fly "Under the Radar".
Be assured they are out there, I recall a comment from someone on ATS last year that had a buddy in the Army, and he told him some of them are as big
as a football field, and completely silent.
Who makes them? Boeing? Lockheed? Mac Douglas?, EG&G? Hughes? or all of them ?? take your pick .