many witness slow moving huge triangular craft

The object was seen by my brother and dozens of other witnesses.  He was employed as an auditor at the time and did not wish his credibility challenged, so he never reported it.  It was however reported on the front page of our local newspaper the following day.  
I am amazed that I can find no reference to this sighting anywhere on the net.   He described the triagular shaped object as blacking out a vast section of the night sky, and travelling very slowly without any sound.  
We are on a flightpath and are used to seeing passenger aircraft at around 25,000ft doing approx 475mph, he told me it moved across the sky at a similar pace, but if it was at a similar height to the passenger aircraft we are used to seeing, then the craft size would be possibly better measured in miles than feet.
Date may be approximate, although the witness does not indicate that fact.  PD