A relative of a passenger aboard missing Malaysia Airlines flight MH370 writes on a balloon at a remembrance event on the one year anniversary of its disappearance in Kuala Lumpur, March 8, 2015. Reuters/Olivia Harris

The Australian Transport Safety Bureau (ATSB), which is leading the underwater search for Malaysia Airlines Flight MH370, announced Wednesday that over 50 percent of the priority search area in the southern Indian Ocean has been scoured. The multi-million dollar search effort for the plane has continued for over a year but has failed to yield clues to the jetliner's whereabouts.

Authorities once again claimed that the current underwater search, which is concentrated in a remote part of the Indian Ocean, would largely be completed by May 2015. The priority search is spread across a 23,166-square-mile area, located about 1,100 miles off the western coast of Australia. However, the search could be delayed if there are any significant delays with vessels, equipment or weather conditions in the area, ATSB said.

Four vessels -- Fugro Discovery, Fugro Equator, Fugro Supporter and GO Phoenix -- are currently involved in the search operation along the seventh arc, which has been previously described as “a thin but long line that includes all the possible points where the last known communication between the aircraft and the communication satellite could have taken place.”

The ATSB said that GO Phoenix, which had departed the port of Fremantle on March 13 after conducting a scheduled resupply visit, resumed search operations last Thursday. The vessel was forced to halt its search for two hours over the weekend due to rough sea conditions. However, it has since continued operations without any more interruptions.

“Overall conditions are expected to continue to be generally favorable during the warmer months,” ATSB said, in the update.

The latest operational update also stated that Fugro Discovery will depart the search area on Wednesday for a scheduled resupply and is expected to arrive in port sometime around April 1. Fugro Equator and Fugro Supporter will also depart the search area this week for a resupply mission.

The Boeing 777-200 went missing on March 8 with 239 people on board during a flight from Kuala Lumpur to Beijing. The search operation has now become the most expensive in aviation history.

Malaysia's transport ministry said, earlier this month, that a new search plan will be implemented after reviewing all the data unearthed so far, if the plane is not found by May 2015.

An interim report released on the one-year anniversary of the plane’s disappearance found that the battery that powered the aircraft's underwater locator beacon had expired over a year before the flight went missing. The 584-page report, also pointed to confusion between Kuala Lumpur air traffic control and their counterparts in Vietnam.

Meanwhile, Andre Milne, a military aviation technology expert, slammed the theory that Flight MH370 went down in the southern Indian Ocean, IBTimes UK reported Tuesday, citing a letter addressed to Australian authorities by Milne. The letter, sent to Prime Minister Tony Abbott, Foreign Affairs Minister Julie Bishop and Defense Minister David Johnston, alleged that the country's claims surrounding MH370 are false and amount to a "criminal act of fabrication of evidence,” and called on the government to prove its theory.