Interesting data points, and all so late in the piece.
A note on the oil rig spotting: The range estimate of 50-70km is way too far to identify an aircraft visually. A bright fire you could see that far no problem, but you would not be able to say that it was an aircraft. And at 50km a fire that bright would be pretty fearsome.
I have been spending my life squinting to see known aircraft at known distances and about ten miles is the limit to make out the shape. You can see strobe lights at 20 nm from a very dark vantage point.
So, what did he see?