Thanks.
One answer …
The gap between the red arcs over south east asia can be explained because those points lie well within the coverage of the Pacific INMARSAT POR.
http://www.inmarsat.com/wp-content/u...ember-2013.jpg
The Malaysian SAR map
https://pbs.twimg.com/media/BiwPWMOCYAAG3ZC.jpg:large
omits red over that area and puts dashed lines in the region under POR coverage.
Thus we assume that the expert teams are satisfied that POR would have picked up the 8:11am ping if it was in that region and that it did not.
Obviously there must be some fuzziness to the ends of the arcs and the POR region because a satellite which is very low over the horizon but still above it may not pick up a signal.
However, when you look at places on the arcs at e.g. the south coast of Vietnam then the POR satellite is at about 10 degrees apparent height and it should have heard a ping.