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Post #5970 I formed the opinion after looking at wind and magnetic variation, that the heading was set to 180°M when the aircraft was about 200NM west of Banda Aceh, Sumatra.
The winds between 10°S & 20°S were from the east, but from 30°S the westerly jet stream started to have and effect, and became the major factor by 40°S.
On top of that was a rapidly changing variation the further south the aircraft progressed, starting at 1°W near the equator and progressing to 30°W near 45°S. The track that was produced included most of that, and it was then that I decided that the heading had been set to 180°M off Aceh.
There had been no mention of 180°M until I posted the graphic.