They started looking in the South China Sea but made their biggest breakthrough following a line that headed straight to the South Pole.
The hunt for Flight MH370 has often stretched the bounds of plausibility, but American and Australian investigators were convinced that the further afield the search went, the closer they would get to solving aviation's biggest mystery.
The deductions that led to yesterday's dramatic developments relied on a series of "pings" that suggested the Malaysia Airlines aircraft flew for hours on a path directly towards the planet's most southerly point.
Almost two weeks after vanishing above the tropics, hopes have increased that wreckage will be recovered from a cold and desolate part of the Indian Ocean north of Antarctica.
Quite how the Beijing-bound Boeing 777 could end up in rough seas 2500km southwest of Perth might remain the subject of debate for months, if not years to come.
Read more of the Herald's Flight 370 coverage today:
• Missing plane: Families face their worst nightmare
• NZ ready to send extra aircraft
• Suspect's father at pains to exude hope in vacuum of hopelessness
But the credit for tracking the plane to the area will be attributed to analysis of hourly data "pings" that continued to be transmitted to a commercial satellite after the plane's communication systems shut down shortly after leaving Kuala Lumpur.
The United States National Transportation Safety Board (NTSB) used the so-called "handshakes" from the aircraft to calculate its most likely route.
The satellite images of the mystery objects. Photo / AMSA
The limitation of the data from the satellite position high above the Indian Ocean meant that two "mirror image" routes on either side of the equator were produced, leading to the establishment by Malaysian authorities of enormous search areas in the northern and southern hemispheres.
Although the NTSB analysts could not be certain, they considered the route towards central Asia far less likely because the flight would have been detected by radar in several different countries.
Asked if the plane carrying 227 passengers and 12 crew headed 180 degrees due south towards the South Pole, a source told the BBC: "That's a reasonable assumption to make."
The analysis also seemed to rule out speculation that the plane might have landed, but continued to contact the satellite.
"Each one of those pings came from a different distance or different angle," said BBC journalist Andy Moore.
"That means ... those transmissions could only have come from a moving aircraft. So that seems to discount the theory that it was parked up on the ground somewhere, the generator was still running and it was sending out those transmissions."
An interfaith event for the missing jet in Kuala Lumpur. Photo / AP
The final contact was made at 8.11am (Malaysian time) on Saturday, March 8 - seven hours and 31 minutes after take-off.
Officials at Australia's Maritime Safety Authority believe the plane ran out of fuel and crashed sometime in the following hour.
That helped in the formulation of a 305,000sq km search zone covering an area bigger than New Zealand after they took control of the hunt in the southern hemisphere on Monday.
Ahead of yesterday's developments it became clear that the focus of the overall search was shifting south.
India reportedly agreed to send surveillance aircraft to help Australian, New Zealand and US planes that were already trying to locate wreckage. Australia was also considering a request by the Chinese military to send assets to the area.
Before the first full day of searching on Wednesday, John Young, general manager at AMSA's emergency response division, compared the hunt to finding a needle in a haystack.
He said it could take weeks.
When Young fronted a press conference beamed live around the world yesterday, he cautioned again against raised expectations.
"We have been in this business of doing search and rescue and using satellite images before, and they do not always turn out to be related to the search, even if they look good," he said.
Photo / AP
If the debris is confirmed to be from MH370, security expert Neil Fergus said a technical malfunction or fire could be ruled out.
"It would in the first instance confirm human intervention," he told the Nine Network.
Other experts believe it is still possible the plane suffered a decompression, rendering the crew and passengers unconscious, and flew on until its fuel was exhausted.
Fergus, who was the director of intelligence at the 2000 Sydney Olympics, hoped sonar buoys dropped from surveillance aircraft would be able to pick up the signal from the plane's black box.
"That will be the key to unravelling this mystery," he said.