Flying high over the North Sea, a mysterious "black triangle" shape flanked by two US fighter jets was spotted by an oil rig worker.

The sighting came as there was a flurry of reports of unusual aircraft, unexplained sonic booms, ear-splitting high-pitched shrieks and fast-moving radar dots around Britain.

For years during the late 80s and early 90s the British Isles seems to have been menaced by these shapes and sounds, with the reports often being branded as UFOs.

It is believed however some of the reports may have been glimpses of a long rumoured 5,000mph hypersonic US spy plane known as the "Aurora".

And in a stroke of extraordinary luck, one of the most compelling accounts of the "black triangle" sightings came from highly trained aircraft spotter Chris Gibson.

He was working on the oil rig Galveston Key in August 1989 and was a trained member of the Royal Observer Corps (ROC), a civil defense unit set up to track and report aircraft over Britain.

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