Could searchers’ sonars have already missed wreckage of Flight 370?

Amid rising frustrations over the expensive, so-far fruitless search for vanished Malaysia Airlines Flight 370, experts are questioning the competence of the company in charge, including whether crews may have passed over the sunken wreckage without even noticing.

Such carping in a small, fiercely competitive and highly specialized industry isn’t unusual — and some of the strongest comments have come from a company whose bid for the lucrative job failed. But others have also criticized what they suspect is shoddy work, inappropriate equipment use and a focus on speed over thoroughness by the Dutch underwater survey company hired by Australia to find the plane that vanished in the Indian Ocean on March 8 last year with 239 people aboard.

There are also calls for the government to release the growing mountain of sonar data collected so far, which skeptics say could show whether searchers have overlooked holes in the dragnet big enough to conceal a fragmented Boeing 777.

Australian authorities say they are confident in the efforts by the company leading the search, Fugro Survey Pty. Ltd. But the second-guessing has grown as time goes by with still no physical trace of the plane.

“It strikes me as odd that you’re hiring a company that doesn’t have the assets, doesn’t have the track record,'' said Steven Saint Amour, an aircraft recovery expert based in Annapolis, Maryland.

Fugro has gotten some confidence from the discovery of an uncharted wreck of a 19th century merchant ship 3,900 metres (12,800 feet) underwater. This bodes well because pieces from the plane would be roughly 10 times as big as the bits of debris searchers found from the wrecked ship, Fugro search director Paul Kennedy said.

Kennedy, who has two decades’ experience in deep-sea sonar towing, dismisses much of the criticism as commercial rivalry and frustration at missing out on a major contract. He also defends his company’s equipment and methods.

“I don’t really buy into those arguments with the other people. We just get on with our work,'' he said.

Some critics argue that Fugro could have easily missed the plane because they say its search ships are misusing 75 kHz sidescan sonar devises called “towfish” that are dragged above a ragged seabed that averages a depth of 4,000 metres (13,000 feet).

The towfish were used to declare a corridor 2,000 metres (6,600 feet) wide clear of wreckage. But some argue that that distance is too far to use such an acoustic system because the sonar image gets worse the farther the signal travels.

The image is said not to degrade with more modern equipment called Synthetic Aperture Sonar, or SAS.

There have been calls to use SAS, but Kennedy calls it a developing technology with some questions about its reliability. Because the search is in such a remote region, Fugro opted for established technology with ready supplies of spare parts.

Australian safety officials say the corridor isn’t too wide, and the equipment was tested thoroughly during sea trials.

Many experts want the raw sonar data released now, or at least reviewed by an outside party to ensure nothing has been overlooked.

Officials have refused, saying that doing the huge amount of work needed to review and analyze the data so it could be understood by the public would be an unwarranted distraction from search duties.

If nothing is found, the search will end next year after a withering 120,000 square kilometres (46,000 square miles) of remote ocean floor up to 6.5 kilometres (4 miles) deep have been combed with sonar and video.