Scanning an endless white-speckled expanse of the blue Andaman Sea, Malaysian air force Captain Fareq Hassan's team of spotters fight turbulence, nausea and mental strain in a seeming "Mission Impossible": to find Flight 370.

"This is not just a needle in a haystack, it's a haystack that gets bigger and shifts under us due to the (ocean's) drift," said Fareq, the flight's navigator.

AFP journalists accompanied fatigued spotters on a search flight to the southeastern Andaman Sea, one of hundreds launched by Malaysia and a number of other nations across vast swathes of Southeast Asian seas and the Indian Ocean in search of any trace of the Boeing 777.

The Casa CN235, a medium-sized twin-prop, has been conducting gruelling eight-hour sorties for a week straight, with a rotating crew scouring more than 20,000 square nautical miles, and finding nothing.

While data from high-tech radars, transponders, and satellites has been brought to bear in the hunt for the missing plane that has gripped the world, the low-tech reality aboard search planes is a mind-numbing, naked-eye affair.

After a 90-minute flight from Kuala Lumpur to the southeastern Andaman Sea far off the coast of Thailand, the crew began looking.

Descending to about 500 feet (152 metres) over the water, the plane settled into a three-hour back-and-forth tracking pattern reminiscent of a lawn being mowed.

"You get dizzy and nauseous trying to track as the sea moves so quickly under you. By the time the flight is over you're close to hallucinating," Sergeant Nor Sarifah Ahmad said over the deafening roar of propellers as turbulence jostled the plane.

The now week-long search for the Boeing 777 jumbo jet initially focused on waters in the South China Sea between Malaysia and Vietnam, where the plane disappeared from radar on March 8.

But, to the torment of passenger's families enduring a long and anxious wait, it has rapidly expanded and shifted.

After Malaysia's leader Najib Razak announced startling new findings, it is now focused on a northern corridor stretching from Thailand to Kazakhstan, and a southern zone from Indonesia towards the southern Indian Ocean.

Najib said Saturday the jet was deliberately diverted off its Kuala Lumpur-Beijing flight path toward the Indian Ocean and parts unknown, and may have flown for nearly seven hours after it disappeared from civilian radar.

The search goes on.

Fareq held a paper map methodically plotting out each day's search route as spotters scanned a seascape sprinkled with deceptive white caps. Only the occasional ship or tiny island broke the monotony.

"Because of the sun's glare, you can't really spot anything blue or white, so we look for baggage or life vests, or something brown or black," said Flight Sergeant Kamarulzaman Jainai.

Yet at 500 feet up, even a fishing barge appears small, let alone spotting a life vest or suitcase.

Fareq said the lack of precise data from multi-million-dollar radar equipment and satellites has hampered operations.

"Yesterday, we were heading to one spot and then received orders to go elsewhere but we don't know why. It throws off our plans," he said.

The palpable tension was punctuated by Kamarulzaman creating a crackling noise while nervously wringing an empty bottle.

But there were light moments as well, as when Kamarulzaman prompted chuckles by jokingly asking Nor Sarifah to massage his neck, stiffened by constant craning.

Ultimately, yet another fruitless flight ended in frustration.

There was a "minor problem with the avionics," Fareq said, announcing the mission would be cut short with about 30 percent of the intended search area yet to be scoured.

"We just have to keep praying."