Aircraft and ships are being diverted to the southern end of the Indian Ocean to verify reports of black box signals...

Flight Commander David Mims returns after searching for MH370. Photo: Reuters

Sweeping over the Indian Ocean at an altitude of less than 100 metres, the crew of the US P8 Poseidon aircraft work silently and attentively on a mission they believe is the most important they have embarked on.

Even on a day considered more favourable than most, one moment there is blinding clarity, the next fog and rain gives the ocean an almost ghostly presence, as visibility shrinks to only a few kilometres.

It is methodical and painstaking work. The pilots direct the plane along a grid, up and back, like a lawnmower. In this case though, the lawn is about 5000 square kilometres and the mower is the world's most sophisticated surveillance aircraft, with a battery of highly classified sensors and cameras scouring the seas for the missing flight MH370.

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Eyes peeled: Warrant Officer Michael Wright keeps watch from an RAAF aircraft. Photo: Reuters

Inside the fuselage are five workstations, each with two large monitors. Crew can switch in an instant between the plane's infrared and electro-optical cameras, its radar and its acoustic sensors designed to locate submarines deep underwater.

A query about the capability of the sensors is met with a smile, and silence. But when the camera zooms in on a suspected piece of debris, it does so with extraordinary speed and sharpness.

Flight Commander David Mims says on this mission, the high-tech equipment is immensely helpful but much reliance is placed on the two spotters who sit in niches towards the front of the Boeing 737.

''At the end of the day, the most important thing is the eyes on the water,'' he says. ''We are looking for just about anything that floats - laminated menus, cushions, anything that holds air or is light. It could be anything from the smallest object to a section of the wing or tail.''

Flight Commander Mims says he has never seen a larger search area in a nine-year career piloting surveillance planes. ''I can't think of a better mission to do,'' he says.

After five hours of searching, the P8 finds nothing other than a naval vessel also tasked to find MH370. But Flight Commander Mims considers the mission a success. ''It's all part of the puzzle we are putting together.''