Still, three separate but fleeting sounds from deep in the ocean, including one today, offer new hope in the hunt for the missing airliner.
The head of the multinational search being conducted off Australia's west coast confirmed that a Chinese ship had picked up electronic pulsing signals twice in a small patch of the search zone, once on Friday and again yesterday.
Today, an Australian ship carrying sophisticated deep-sea sound equipment picked up a third signal in a different part of the massive search area.
Retired Australian Air Chief Marshall Angus Houston, who is coordinating the search, says the next step "is to determine the significance" of the sounds.
Copyright 2014 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.