Eleven aircraft and 12 ships continued to search the Indian Ocean for the missing Malaysian jet Friday, more than five weeks after it mysteriously disappeared.
The Australian Maritime Safety Authority planned a visual search of a 3,223-square-mile area.
Officials hope to find physical evidence they are searching in the right spot for the Boeing 777, which vanished March 8 with 239 on board on a flight from Kuala Lumpur, Malaysia, to Beijing.
So far, not a single piece of debris has been recovered.
Overnight an unmanned submarine from the U.S. Navy, the Bluefin-21, completed a mission in the underwater search and began another. The sub has so far covered 68 square miles of ocean floor using sonar.
The Bluefin is searching water 15,000 feet deep. Sound-locating equipment had earlier picked up sounds consistent with an airplane's black box, but it has since gone silent.
Radar and satellite data show the plane flew far off-course and would have run out of fuel in a remote section of the Indian Ocean. Planes and ships have been scouring the ocean surface for a month, to no avail.
At a news conference on Thursday, Malaysia's defense minister, Hishamuddin Hussein, confirmed the search would continue through the weekend but acknowledged that officials would have to rethink their strategy at some point.
"There will come a time when we need to regroup and reconsider, but in any event, the search will always continue. It's just a matter of approach," he said in Kuala Lumpur.