“The so called U turn over Long Island was a turn probably programmed into the plane’s FMS according to the clearance. The last fix prior to Islip is Calverton VOR which is the normal routing in the New York area coming from the southwest. The FMS and autopilot then just held that heading after the turn toward ISP until plane ran out of fuel.”
This makes sense except for two things. The first is it appears to make a beeline back to 0A9 after the big turn: could the pilot have programmed 0A9 as the last waypoint, possibly to see if he had the fuel to return while on his way to Islip, intending to remove it from the plan once he had a good idea?
The second point is if the airplane was indeed holding heading after the turn, wouldn’t there be some small changes of course in the final leg, subject to changes in winds aloft speeds and directions? Again, it appears to be a solidly held course until flameout.