Last Satcom 'ping' error radius
The arc's showing north and south potential locations for the final SATCOM 'ping' are only very approximate guides. Added to this, in the most extreme scenario the final 'ping' could have been sent up to 59 mins before the aircraft had actually landed or its engines were shutdown or had flamed out. (I.E. final event could potentially occur only 1 minute before the next ping was due to be transmitted)
This being the case we need to add that extra 59mins potential range, so at 480kts add another 480nm!
Also if still at altitude and the engines flamed out on this 59th minute then at FL390 you could add an additional glide distance of a further 150nm. (still air) Therefore, in this extreme scenario there is (very roughly) a potential further 630nm of omni directional error. Effectively you can redraw these arc points, giving them a 630nm error radius (or put another way 1260nm wide!) Perhaps someone could apply these distance and post the revised arc's.