After nearly two years of extensive search for the missing Malaysia Airlines Flight MH370 in the southern Indian Ocean, the organization leading the hunt is skeptical of the outcome, according to a Bloomberg report.

Martin Dolan, head of the Australian Transport Safety Bureau, said Tuesday that there is “a possibility” that the search for the missing Boeing 777-200 “will not succeed,” Bloomberg reported.

Flight MH370 went missing on March 8, 2014, with 239 people on board while on its way from Kuala Lumpur to Beijing. So far, the first and only piece of physical evidence to be recovered from the plane is a flaperon that washed ashore on France's Réunion Island in the Indian Ocean — about 2,300 miles away from the current search area — in July 2015. The multimillion-dollar search for the plane has yielded no concrete clues so far.

“There’s always this question: Have we missed something?” Dolan, 58, reportedly said at his office in Canberra. “That’s the sort of thing that will occasionally keep me awake at night.”

Dolan said the search for the jet is expected to end in June if no fresh clues are found after four search vessels finish scouring 46,330 square miles of the southern Indian Ocean. Search vessels have scanned most of the area in the search zone with no sign of the missing jet, leading authorities to believe that the world’s most expensive search for a commercial airliner — which has so far cost about $130 million — may fail.

“We were ready for most things, but MH370 has been unpredictable all the way through,” Dolan said, according to Bloomberg. “It’s a possibility we will not succeed.”

Late last month, Dolan told News Online, an Australian website, that search crews are retracing their steps to be sure that they had not missed the plane, which is believed to be resting on the floor of the southern Indian Ocean. Dolan added that the difficult terrain on the ocean floor did not always allow the vessels to get a “good enough sonar image.”

On March 8, 2014, air-traffic controllers lost contact with Flight MH370 less than an hour after it took off from Kuala Lumpur as it approached Vietnamese airspace. According to military radar, the plane took a left turn, looped back across Malaysia and headed northwest up the Straits of Malacca. However, investigators believe the plane then headed south to finally crash in a remote section of the Indian Ocean.

Following the disaster, the International Civil Aviation Organization (ICAO) has pushed for commercial aircraft to report their positions every 15 minutes. The agency also issued a proposal from the European Union that will allow underwater locator beacons inside black boxes to last for 90 days instead of the current 30.

Malaysia is reportedly expected to release a report on the second anniversary of the plane’s disappearance on March 8.