About 10 ,yrs ago My wife and I were returning from holiday in Cyprus and were in an plane about 30,000ft above Austria . My wife said " look at this " . I looked out of the window and there at a distance that I would judge to be about a mile away was a black triangular craft . It was like a triangle stood on its base point upper most. It move slowly form the front of the plane to some way behind ,still staying about the same distance away . It then ,without stopping or changing direction , turned through 180 degrees and flew back in the same direction as us but at an incredible speed . It was gone in seconds. We were not the only ones to see this . Every one on that side of the plane was looking at it as were as many other as could get to a window .The object must have been enormous because to us it looked to be about 4 inches tall from the distance of a mile