Following a four-month break, the search is on again for Malaysia Airlines Flight MH370, the Boeing 777 that disappeared March 8 in the largest aviation mystery of the year and perhaps ever. The search for MH370 is expected to take another year, according to Australian authorities leading the search operation.

“All the available data indicates the aircraft entered the sea close to a long but narrow arc of the southern Indian Ocean,” according to the Australian Transport Safety Bureau, the investigatory body in charge of the search. “The complexities surrounding the search cannot be understated. It involves vast areas of the Indian Ocean with only limited known data and aircraft flight information. While it is impossible to determine with certainty where the aircraft may have entered the water, all the available data and analysis indicates a highly probable search area close to a long but narrow arc of the southern Indian Ocean.”

A vessel known as the GO Phoenix was contracted by the Malaysian government to search for the doomed MH370. The 239 people on board the Kualu Lumpur-to-Beijing Malaysia Airlines flight were presumed dead, most of them Chinese. There were 50 Malaysians onboard; 13 other nationalities had less than 10 casualties each.

“The vessel GO Phoenix, with equipment and experts provided by Phoenix International, has arrived in the search area in the southern Indian Ocean, and commenced underwater search operations,” the Australian Transport Safety Bureau said in a statement, according to Al Arabiya News. The ship will search the southern Indian Ocean by using sonar to scan the ocean floor as far as 3.7 miles down for signs of the missing plane.  

MH370 was the first of two air disasters to hit Malaysia Airlines. In July, Malaysia Airlines Flight 17 crashed in Ukraine, killing all 298 people onboard, including 193 Dutch nationals. Western intelligence sources said the Amsterdam-to-Kuala Lumpur flight was shot down by pro-Russian separatists battling Ukrainian forces in the eastern part of the country. The separatists denied downing the plane.