The multinational effort to find the wreckage of MH370, which disappeared 45 days ago, has completed two-thirds of the search in the most likely location.
Yesterday, the Bluefin-21 started its ninth mission but so far has found nothing of interest.
The underwater search area is focused on a 10km radius around the second pinger detection of the black boxes on April 8.
There were, however, three other firm pinger detections and two that faded out.
Sources in Washington have told _The West Australian _that there are three Boeing 747 freighters on standby in the US to bring out additional underwater search equipment for either a widening of the search or when MH370 is found.
Yesterday, Australia's Ambassador to the US, Kim Beazley, said private contractors and more underwater search vehicles could soon be used in the search.
The air search might be adjusted, Mr Beazley told CNN's Sunday morning program State of the Union.
"All of these sorts of things will be on the table if nothing is found in the next few days," Mr Beazley said.
Yesterday, 10 military aircraft and 11 ships took part in the search.
The Australian Maritime Safety Authority planned a visual search area totalling about 49,491sqkm with the centre of the area about 1741km north-west of Perth.