ABOARD US NAVY P-8 POSEIDON, Indian Ocean — Of all the 20 aircraft and ships out scouring the vast Indian Ocean for debris from Malaysia Airlines Flight MH370, the U.S. Navy’s P-8 Poseidon seems perhaps the most likely to help unlock modern aviation’s most confounding mystery.

Five workstations lining the fuselage display high-definition video from the top-secret sensors that make this one of the most sophisticated surveillance planes in the world.

But the latest mission in the three-week hunt — five luckless hours skimming as low as 300 feet above the wave tops — only served to underscore the enormity of the challenge facing the international search team.

“This is my first time in the Indian Ocean and it is unquestionably the most untouched piece of water I have ever seen,” U.S. Navy Lieutenant Commander David Mims, the plane’s pilot, told Reuters during a search flight this week.

“It’s rare to come out and not see any land mass, not see any shipping traffic. There’s nothing,” he said. “It’s weird.”

The United States, China, Australia, New Zealand, South Korea and Japan are all scouring an area some 1,200 miles west of the Australian city of Perth, where investigators believe the Boeing 777 carrying 239 people came down.

So far, the search has turned up only fishing rubbish and other flotsam. It has been halted several times by bad weather in the search area.

Two Poseidons are engaged in the search. Costing around $175 million, the aircraft is armed with cameras, infra-red and radar sensors that are fine-tuned to detect enemy submarines hiding under the ocean surface.

But despite its high-tech equipment, much of the searching is visual — crew members peering out a window.

“I’m a pretty optimistic guy by nature,” said Petty Officer Michael Herman, perched in front of a porthole staring out into the foggy sea. “But yeah, this is tough.”

The Poseidons operate alongside a pair of Chinese Il-76 military transport planes at Perth International Airport. They are kept under tight security, including a round-the-clock armed rapid response team.

The plane is so top-secret that a Reuters journalist given a rare berth was stripped of all electronic devices and barred from taking pictures.

The technology is impressive. Sitting at a pair of monitors stacked one atop the other, Petty Officer Julio Cerpa operates a panoramic camera that quickly zooms in on distant patches of ocean with great clarity.

An infrared version of the same camera feed cuts through the haze of fog surrounding the plane, offering a polarised and somewhat nightmarish view of the search area.

About two hours into the search zone, the monotony of peering out a window or at a computer screen is starting to wear on the crew.

Petty Officer Sam Judd begins a slow climb up his seat back that will eventually see him perched atop it. Cerpa’s hands turn his workstation into the world’s most expensive drum kit.

And then the plane begins to ascend back to 30,000 feet having found nothing. The total trip, including flying time to reach the search zone, is around 10 hours.

To an outsider, the experience can seem frustrating, but the crew maintains a remarkably optimistic outlook. Even a trip that finds nothing rules out a part of the search zone, and is thus an important part of finding the wreckage, says Mims, the pilot.

“Being this far into the search process and having this much ocean to cover definitely makes it a challenging evolution,” he says. “But if it’s in our area, I think the probability of finding it is high.”