“Also, the Citation apparently followed the lateral track of an instrument approach, turning toward and then overflying its destination, New York Long Island McArthur Airport (KISP). But it flew the “approach” at 34,000 feet and continued on a consistent track until apparently running out of fuel and spiraling to the ground at a high rate of descent.”
I disagree with your track analysis.
The airplane followed the flight plan/cleared path. The last part of the plan was SARDI DCT CCC DCT KISP. The airplane smart turned from SARDI-CCC to CCC-KISP, it didn’t line up with an approach. After passing KISP it followed an extended, great circle path from CCC-KISP. If you put that on ForeFlight, and put KISP-0A9 on there as well you’ll see a divergence of about 1º. It is simply an incredible coincidence that it is so close.
I think my theory satisfies Occam’s Razor as well.