There's a particularly tantalising reason why the wreckage of Malaysia Airlines flight MH370 may indeed be found inside the proposed new search area at 35 degrees south in the southern Indian Ocean.
It's the lack of any debris from the plane found on Australia's west coast.
Other than a small towelette in Malaysia Airlines packaging found on a WA beach in 2015 — which may or may not have come from MH370 — every piece of debris known to have come from the missing plane washed up on the east coast of Africa, or nearby islands.
This is significant, given Australian investigators believe there were five possible autopilot control modes the plane could have been on at the time it ran out of fuel and crashed into the ocean.
Calculations based on four of those settings point to a crash site further south (36-39 degrees south) or further north (33-34 degrees south), where the ocean currents in the days after the plane disappeared ran in an easterly direction, and would be expected to wash at least some debris towards Australia.
One source close to the investigation says only one of the five auto pilot settings — constant magnetic heading (CMH) — would lead to a crash site at 35S, where the ocean current at the time ran in the opposite direction, towards Africa.
Nevertheless, other evidence in the weeks and months after the plane disappeared — namely the satellite "pings" picked up from the aircraft by Britain's Inmarsat satellite — prompted the Australian-led search team to focus on a 120,000-square-kilometre area around 36 degrees or further south, a search which ultimately proved fruitless.
Only now, since the examination of the various debris and studies on ocean drift patterns, has the likely wreck site shifted north to an area around 35 degrees south, straddling the imaginary line known as the "seventh arc" — which shows possible locations of the plane at the time of the seventh "ping".
Debris discovery location leaves 35S the 'only option'
The Malaysian Government this week confirmed it had signed an agreement to pay a US seabed exploration firm Ocean Infinity between $20 million and $70 million if it finds the missing aircraft within 90 days of embarking on a new search.
Its search ship Seabed Constructor is already heading to the new search zone and will begin scouring the ocean floor as early as next week.
Ocean Infinity is confident of finding the plane if indeed it is inside the search area.
"We can roughly cover 1,200 square kilometres a day," chief executive Oliver Plunkett said.
"Which means that we will finish the first 25,000 within first three to four weeks of the search."
Dr David Griffin, an Australian oceanographer at the CSIRO, led the drift analysis that last year helped narrow down the search zone to an area no bigger than 25,000 square kilometres, where Ocean Infinity will focus its search.
"The oceanographic reason for why 35 [degrees south] is more likely than say 34, or 33, or 32, is that at all those latitudes the current is going to the east," Dr Griffin said.
"So if the crash had been in any of those latitudes then there'd be a high chance of at least one or two things turning up in Australia. Whereas there've been 20 or 30 or so items turned up in Africa, and not a single one come to Australia.
"Once you start looking in the vicinity of 36 to 32, then 35 is the only option."
Interest revived in dismissed French satellite images
The autopilot settings and the discovery of debris in Africa — including a flaperon confirmed to have come from flight MH370 — are not the only evidence supporting the theory that the missing plane is in the proposed new search zone, north of the area already searched.
French satellite images first seen in March 2014, a week or so after the plane disappeared, showed white objects in this same area, at 35S.
At the time the objects were dismissed as unimportant.
Other photos had showed similar "blobs" elsewhere in the southern Indian Ocean, many of which were later ruled out as shipping containers, general ocean rubbish or even pods of dolphins.
The French photos were also of poor quality, making it almost impossible to see what the objects were.
But as other evidence began to point further north — the results of the CSIRO drift study and the discovery of more debris linked to the missing plane — investigators suddenly remembered the satellite images.
They asked the French for better copies. And only then did they realise the photos were more significant than first thought.
"When anyone looks at them you think, if they're not bits of plane, what are they? Because for lots of those other objects you can find an explanation, but for these you can't," Dr Griffin said.
Finding wreck now is unlikely to solve the mystery
The drift analysis included retrospective calculations to gauge where the objects might have been in the hours after MH370 disappeared. And sure enough, it was around 35S, the new zone where Ocean Infinity is preparing to search.
When Ocean Infinity reaches its destination next week, it won't be the first time that seabed vessels have searched along the seventh arc at 35S.
In the weeks after MH370 first disappeared, searchers scoured the ocean floor along the same trajectory from about 32 to 39 degrees south, and found nothing.
But Dr Griffin says that search was very narrow — barely 20 kilometres either side of the arc.
The new search will scan a wider area. Although evidence including the plane's flaperon, which was found in Tanzania, supports the theory that the aircraft went through a rapid descent once it ran out of fuel and landed close to the "seventh arc".
Examination of the flaperon indicates it was retracted at the time of impact, debunking the theory that the pilot was still in control and trying to glide the plane as far as possible before it crashed.
Evidence in a report by the Australian Transport Safety Bureau in late 2016 assessing satellite communications from the plane, known as the Doppler Shift Burst Frequency Offset, is also consistent with a rapid descent and the wreck site being closer to the seventh arc.
The new search is due to begin next week. To qualify for its multi-million-dollar pay day, Ocean Infinity must find the debris field or the flight recorders within 90 days.
And even if the plane is found, there may never be a satisfactory explanation for why MH370 disappeared.
"If they find it, will it be financially viable to bring it up? And even if they did, what information could it give us?" aviation specialist Trevor Jensen said.
"The flight recorders, the voice recorders, would all be so damaged now."