Now Julian Schmidt has emailed us to say he believes they are not of alien origin - but man made.
He said: "I have been studying these Black Triangle phenomena since 1987, when my three sons and I witnessed one flying low and slow across our house one night.
"I distinctly heard a low pitched humming sound being made by the craft.
"The sound reminded me of a 600 amp 60 hertz transformer under maximum load.
"I am an Electronic Technician and have experience with state of the art technology.
"It is my belief that these craft use some sort of fusion reactor that must be shielded with a very powerful electromagnetic field. Similar to the Tokamak Fusion technology.
"I do not believe that these craft are piloted by alien beings. This technology may also be able to cancel the effects of gravity and drag. Hence the incredible rates of acceleration.
"A friend of mine has a brother working for the NSA. All he will tell me is that they have technology 20 years in advance of what we civilians have access to.
"I believe the United States operates these 'Black Triangles'. It is not so hard to imagine when you consider the annual military budget is nearly 600 billion dollars!