Question: How erratic could the flight path be back to LKP? All I have seen to date is MM43's nice bank angle arc analyses, so this seems like a new proposition to me
Very good question!
theoretically it could be very erratic. Depends really on the mode how and why it came down. If we had a radar track of the final 5 minutes we might already have a much better idea what happened (besides obviously being able to locate the wreckage much easier).
However, assuming control of the plane got lost at altitude, keeping a defined flight path was probably rather low on the agenda of the pilots.
JD-EE:
This energy loss is really what is most mysterious to me. As you said 210t with almost 500kts at 35000ft is a HUGE amount of emergy. This obviously has been dissipated within only 5min to a very low energy state.
(maybe 100 -150kts at 0ft). Doing this without breaking up the aircraft isn't easy.