The team searching for missing Malaysia Airlines Flight MH370 in the vastness of the Indian Ocean off Western Australia is working with the slenderest of clues painstakingly drawn from minute fragments of evidence. (The Australian Transport Safety Bureau released its latest review of evidence this week.)

Over the past two years the searchers have been accused of everything from incompetence to malfeasance, and of overseeing a giant cover-up. But their harshest critics continue to conflate two key questions: who was responsible for the disappearance of the Boeing 777 with its 239 passengers and crew, and where is the aircraft now?

A 2014 report, variously described as originating from the FBI or Malaysian Police, said that MH370 pilot Zaharhie Ahmad Shah had previously plotted a course down into the southern Indian Ocean on a simulator. The searchers don’t dispute that the pilot may have been responsible for the disappearance but the likely crash area wasn’t defined by hypotheses about what Captain Zaharie might’ve done. Instead, the likely location was identified after months of work by the Defence Science and Technology Group, which analysed signals transmitted automatically by the satellite communications system on the jet as it made its lonely flight southward, and calculated when it would’ve run out of fuel.

Just after midnight on March 8, 2014, MH370 took off from Kuala Lumpur headed for Beijing with a final radio message bidding the KL tower ‘goodnight’. The jet didn’t arrive, and it was believed to have vanished along its scheduled route.

As MH370 flew, it automatically received or sent routine signals as ‘handshakes’ with a satellite linked to a ground station in Perth. That system worked independently from others controlled by the crew and was designed to provide data about the state of parts such as the engines. Technicians from Inmarsat discovered the ‘handshakes’ and realised that the jet must have flown on for hours. Two satellite phone calls made to MH370 had gone unanswered but analysis of the signals indicated the jet was heading south. Malaysian military radar had seen the jet making two turns which took it back over the Malaysian Peninsula. It then became clear that MH370 made at least one more turn to head south. Those three turns would have to have been made by a pilot.

With almost nothing else to go on, scientists were left to calculate the time it took for the signals to travel between the aircraft and the satellite, and hence to work out where MH370 was at that time. Two signals from the aircraft were different. One came early on, when the satellite communications system came back to life after a period of silence. And then, after the six hourly ‘handshakes’ came a signal which was out of sequence and, again, seemed to be the result of a power failure to the satellite communications system. The investigators believe that happened at 8:19am (WA time) on 9 March, after the aircraft ran out of fuel and the two giant engines flamed out—the left engine first and the right up to 15 minutes later.

Simulations by Boeing indicate that once the engines lost power, MH370 would likely have slowed and lost lift. Its nose would have dropped and it would have descended in a ‘phugoid‘ motion in a series of swoops. It’s likely that the jet fell very fast—up to 25,000 feet a minute.

As it gathered speed, it would gain lift and climb again. As that speed fell off, its nose would have dropped rapidly once more, the aircraft falling into another steep dive. That process is likely to have been repeated until it hit the water, probably with one wing down, according to Boeing. The impact would have been catastrophic; the discovery of ­pieces of the aircraft’s interior indicates that it broke up on impact.

Critics of the search strategy suggest that once MH370 ran out of fuel, the pilot glided it ­for 100 nautical miles and ditched it in the ocean far from the search area. But the Australian Transport Safety Bureau says analysis of the signals most closely matches a scenario in which there was no pilot at the controls at the end of the flight.

Examination of a crucial piece of wreckage indicates that when MH370 slammed into the ocean, a wing flap was in a “cruise” position and not lowered for a landing as it would have been had there been a pilot at the controls. The flap was likely torn from the jet as it hit the water and drifted for more than a year to the coast of Tanzania in East Africa. It was part of the right wing ­positioned next to another control surface known as a “flaperon” which washed up on Réunion Island.

The drift of wreckage allowed for a second line of investigation. CSIRO have been conducting experiments to work out where wreckage that drifted to Africa began its journey. Significantly, the conclusions about the likely location overlap those of the Defence scientists, just north of the current search area. Given that it’s consistent with two independent lines of enquiry, that’s now the target, if money’s found to continue the search.

Media reports this week have erroneously referred to a ‘new’ search area, lying north of that searched so far. In fact, the new area of interest lies along the seventh of a series of arcs calculated from the satellite signals. The scientists believe the aircraft is along that seventh arc, which continues through the major area already searched. It was one of the first areas covered but the view now is that search wasn’t wide enough and should be expanded by about 25 nautical miles on each side of the arc. That’d mean an additional 25,000 square kilometres to be covered and would, based on costs so far, require an additional $50 million.

The suggested area covers more rugged sea floor extending to the Broken Ridge escarpment. At up to 6 kilometres deep, it’s below the reach of the autonomous underwater vehicle now being used, though suitable equipment is available for hire. Mathematicians now estimate the chance of finding MH370 there as at least 85%, but it seems unlikely that Australia, Malaysia or China will put up the extra money. We might never definitively know where MH370 ended up.