Visual sighting of aircraft over long distances
When I was a spotter and listened to VHF radio from my home in Glasgow, elevation 100' or so I could see contrails over Belfast, a distance of approx 100 nautical miles. The trails were very low to the horizon (<10°) but very definitely over Belfast since there was no traffic over Prestwick. This was late daylight, winter, high pressure so cloudless and highlighted by a low sun.
So my point is the Kiwi oil worker could have seen at night a bright light or fire over a considerable distance, as he described. Whether that was the missing 777 remains to be seen.