From earlier reports on here there appear to be many assets out there. I have no doubt they are all very busy. But with nothing found at this late stage, they MUST ALL have been looking in the wrong place (or, and this doesn't bear thinking about) someone's search has been compromised.
From a SAR standpoint, is there ONE AGENCY in overall command and control? If you're about to say yes, think very carefully about the question. There are very great difficulties with this particular SAR effort and more so than with any other I have known. It is not only multi-national but the forces also cross ideological divides. Trying to coordinate different forces from ONE nation can be fraught with difficulties, but in this case, in addition to coordinating egos, forces from many nations bring different priorities, manifestos and other differences. The whole operation risks being thwarted by inability and unwillingness to fall in line.
The effort in theory is relatively simple: Construct a grid based on a variety of last known positions, CAREFULLY calculated forward throw ballistics, etc, etc. Then, "You, you and you look HERE... and you lot and you look THERE." etc, etc. With creeping line ahead and expanding square search patterns sweeping into the less plausible grid squares, something must be found soon given a sufficiently large number of suitably-employed assets. And whoever finds something first becomes Scene of Action Commander. Because time has gone by and we're now into replacement of search personnel, a team is needed to compile and maintain a roster. Diplomatic effort, particularly, is needed here to smooth the way for effective command, control and communications. Without a competent central command centre, everyone will continue to rush around like headless chickens.
Sure, under the status quo, eventually, something will be found. It could be better than this.