JD-EE
Actually a 20nm circle is a little off beam. Something more akin to a cardioid might be the correct figure to search within. The initial point for the cardioid would be last known position.
That would probably be the ideal approach, assuming that a 180° turn at cruise speed would already consume 5-10nm, thus reducing the effective range in the opposite direction to some extent.
So a cardioid ranging 25nm in flight direction and roughly 15nm in opposite direction from LKP would proably have the highest likelyhood of a hit.
But the concentric circle of 20nm seems to me a pragmatic approach with a very good probability compared to the -from my very humble point of view- somewhat odd search areas of the first three phases.
From my perspective thzey ignored the general Flight Dynamics to much and relied too much on the very unreliable (due to unpredictable relatively high speed currents) backdrift analysis.
So I remain confident this time.