An underwater drone is continuing to scan the Indian Ocean seabed for the missing Malaysia Airlines jet, despite failing to find any sign of the aircraft this week.
The Bluefin-21 underwater drone has been deployed for a fifth time after completing another fruitless mission overnight.
Friday's search is expected to cover 51,870 square kilometres and will involve up to 11 military aircraft and 12 ships, AAP reports.
Australian Prime Minister Tony Abbott has said a rethink on the search will be needed if the Bluefin-21, which has so far searched about 110 square kilometres since its first deployment on Monday, failed to find the wreckage of flight MH370.
The Joint Agency Co-ordination Centre (JACC) has said the search will continue for the next three days, but has not elaborated on activities after that.
The search is focusing on seabed more than 2000km northwest of Perth in the same area where an oil slick was found on 13 April. However, JAAC's preliminary analysis of the slick showed it was not aircraft engine oil or hydraulic fluid.
Mr Abbott said he is confident that the search is focused on the right place, based on acoustic signals detected by a pinger locator towed by the Australian naval vessel Ocean Shield on 5 and 8 April.
Saturday marks six weeks since flight MH370, carrying 239 passengers and crew, disappeared on 8 March.