Perth, Australia (CNN) -- Four weeks to the day since Malaysia Airlines Flight 370 went missing, the search is set to continue Saturday -- both on the surface of the southern Indian Ocean and deep below it.

Time is fast ticking down to find the missing Boeing 777's locator pingers: If functioning as expected, their batteries will run out of juice Monday.

The British Royal Navy survey ship HMS Echo and the Australian naval supply ship Ocean Shield began scouring about 6,500 feet to 13,000 feet deep on the ocean floor on Friday along a single 150-mile (240-kilometer) track, said retired Air Chief Marshal Angus Houston, the head of the Australian agency coordinating the search.

The Ocean Shield has high-tech gear borrowed from the United States. That includes a Bluefin-21, which can scour the ocean floor for wreckage, and a Towed Pinger Locator 25, with its underwater microphone to detect pings from the jet's voice and data recorders as deep as 20,000 feet (6,100 meters).

"It is a very slow proceeding," U.S. Navy Capt. Mark M. Matthews said of the second tool, which is towed behind a vessel typically moving at 1 to 5 knots.

Said Bill Schofield, an Australian scientist who worked on developing flight data recorders: "If they do find it, I think it'll be remarkable."

Up to 11 military planes and four civilian aircraft -- in addition for 11 ships -- will be looking Saturday for any sign of Flight 370, according to the Australian government.

The search area will be just under 84,000 square miles (217,000 square kilometers), which is slightly less than the area searched Friday, and will focus some 1,050 miles northwest of Perth. This is about 50 miles further from the western Australian city than was the case a day earlier.

Is this the right spot? Will they find anything? So far, all efforts to locate signs of the airliner have proven unsuccessful. Still, those involved have vowed to keep trying.