At a glance: How search crews plan to hunt for Malaysia Airlines Flight 370

Map shows search areas for missing Malaysia Airlines missing jet.; 2c x 5 inches; 96.3 mm x 127 mm;

Map shows search areas for missing Malaysia Airlines missing jet.; 2c x 5 inches; 96.3 mm x 127 mm;  (The Associated Press)

The search for missing Malaysia Airlines Flight 370 resumed Monday in a remote part of the Indian Ocean, far off Australia's west coast. Here's a rundown of the operation to look for the jet, which inexplicably vanished nearly seven months ago:



Three ships will take part in the search: the GO Phoenix, provided by Malaysia's government, and the Equator and Discovery, provided by Dutch contractor Fugro. The GO Phoenix was first on the scene, with the Discovery joining in later this month. The Equator is still mapping areas of the search zone and will join the hunt once that is complete, likely at the end of the month.



The search zone is about 1,800 kilometers (1,100 miles) off Australia's west coast. This 60,000-square kilometer (23,000-square mile) area lies along what is known as the "seventh arc" — a stretch of ocean where investigators believe the aircraft ran out of fuel and crashed, based largely on an analysis of transmissions between the plane and a satellite. The water ranges from 600 meters (2,000 feet) to 6.5 kilometers (4 miles) deep — the equivalent of three-quarters of the height of Mount Everest. The average depth is 4 kilometers (2.5 miles). The terrain is mountainous, with ridges and volcanoes jutting out of the seabed and deep crevasses providing sharp, sudden drop-offs.



Each ship will have a crew of 25 to 35 people working around the clock. The teams can stay at sea for up to 30 days before heading back to shore to refuel, resupply and rotate the crew. It takes up to six days just to travel between the search area and the Australian coast, the closest land.



Each ship will use towfish, underwater vessels equipped with sonar that create images of the ocean floor. The sonar on the towfish has a spread of 1.5 kilometers (1 mile) on each side. The Fugro ships will use the EdgeTech DT-1 towfish, and the GO Phoenix will use the SLH ProSAS-60 towfish.

The towfish are attached to the ships by thick cables up to 10 kilometers (6 miles) long. They are dragged slowly through the water about 100 meters (330 feet) above the seabed. If a towfish detects something of interest, it is hauled up and fitted with a video camera, then lowered back down to film the seabed. The towfish are also equipped with sensors that can detect the presence of jet fuel.



Unlike the Bluefin-21, the underwater vehicle used in the initial search, the towfish can transmit data back to the ship in real time, which means the crew should quickly spot anything unusual. A separate team in Perth will also review the data, to ensure those on board haven't missed anything.