Observations
Usually seen at night, witnesses report sightings of huge, dark triangular shapes, moving across the sky, blotting out the stars. Sometimes they are entirely dark, sometimes they show lights. During the early 1990's there was a wave of over 4,000 sightings across the north of England, Belgium, Holland and Germany, with fighters being sent to intercept the craft. Sightings have also been reported from the USA, where winesses describe similar events.

What could they be?
As one might expect, every sort of theory has been tried to explain the phenomena, but no-one knows. The UFO brigade have typically jumped on board, but most of their theories are the 'content free noise' variety. More credible is the theory that these are earth-based aircraft of some description. There have been many sightings of dark, triangular aircraft over the years, which may or may nor be attributable to projects such as 'Aurora', TR3, Astra and others. It's possible that the new sightings are of a 'stealth blimp' - a lighter than air craft of huge proportions. Certainly, such a vehicle would be attarctive to the military. It would have large cargo carrying capacity, could loiter for long periods at altitude for reconnaiscance, and may employ exotic technologies for propulsion and camouflage. Many sightings have described a form of 'visual stealth' where it appeared that the craft was displaying an image of the sky above it in order to mask it's shape and size.

It could also be related to the mythical 'Senior Citizen' programme to develop a high speed, stealthy, VTOL transport aircraft. As usual, the people who know are saying nothing, leaving an empty space inhabited by all kinds of theories, which serve to create confusion, misinformation and effectively conceal their true identity.

'Stealth Blimp' - Click for larger image