Originally Posted by
BWV 988
Though we only have information about the last MH370 ping at 0:11 UTC, a massive search operation in the middle of a remote ocean would only be carried out if the (unknown) hourly pings made that area feasible.
As the flight originated near the equator, a mirror track to the north would also correlate with the returns, then leading to a last ping area in northern China close to the Gobi desert. Bearings more to the west, however, would appear less likely, given ping data is coherent.
Though the flight originated "near" the equator, last known contact was not on the equator, and you have to account for that when making a mirror track. They are working off the tracks that end up roughly at 40S and 83E to 87E, which would be 2700 NM from the satellite epicenter at heading 155 to 160. Last known position is at heading 78. That would put the symmetrical site at 2700 NM due north (heading 356 to 1) - near Aral Sea in Kazakhstan/Uzbekistan/Turkmenistan.
In addition, current search is based on the premise that the debris drifted substantially to the southeast in two weeks since the crash. They are searching way outside the arcs by now.
One of the reasons why Australians are looking in the exact spot where they are looking is simple. It does not make sense to look further southwest, because the aircraft barely had time or fuel to get to where they are looking as is. On the other hand, it does not make sense to look further northeast, because Australians have a powerful over-the-horizon radar system (Jindalee) with coverage that extends almost to 30S 90E, and, if MH370 had gone down further northeast, it probably would have been picked up. This leaves a pretty narrow area where they could be looking.