Just days after the official search for missing Malaysia Airlines flight MH370 was suspended, an air crash investigator has spoken out about what he believes happened in 2014.
The Boeing 777 vanished while flying from Kuala Lumpur to Beijing with 239 passengers on board, including Christchurch man Paul Weeks.
Veteran pilot and accident investigator John Cox says there are a couple of viable theories that experts have proposed.
"There's not a lot of disagreement to what happened in the early parts of the flight," Mr Cox told RadioLIVE's The Long Lunch.
"It's the last 8-10 minutes where there's some controversy and some differences in opinion."
When Carly Flynn asked what the pilot's own theory is, Cox gave a chilling response.
"It flew so carefully along the border between Thailand and Malaysia, across Penang and then up the straits right virtually in the middle to just a point where the radar no longer reached. All of those indicate a deliberate act."
"I think it's compelling evidence that it was in fact a deliberate act."
Cox told RadioLIVE that the most likely candidate was Captain Zaharie Ahmad Shah.
The flight's detour over the Malaysian state of Penang was the captain's home town.
After flying over Penang, Cox explained that the aircraft flew across the Indian Ocean for several hours up to a point of inevitable fuel exhaustion.
This is where many of the divisive theories begin.
"We don't have enough data, enough evidence, to conclusively know. The theories are all at this point incomplete."
One theory is that the captain was still alive and control ditched the aircraft in the Indian Ocean. Another is that the aircraft impacted the water at high speeds.
"We really don't have enough information to know which one of those two occurred," he said.
Though the search is now suspended, Cox said that there are investigations that could be done to determine "a higher likelihood" of which situation actually transpired.
Further conspiracy theories have emerged following the incident. One of those is based around the 200 kilograms of lithium-ion batteries that were in the cargo hold of the aircraft. Some believe that this may have caused an explosion or fire, which could explain why the plane diverted from course.
But Cox, who's been studying lithium batteries for the past five years, told RadioLIVE that the theory should be laid to rest.
"In every case of a lithium battery fire, the crew has been able to make contact with air traffic control and at least attempt a diversion.
"That didn't happen here."
He explained that the painstakingly "deliberate" course taken along the Thai and Malaysian border illustrates that it is highly unlikely that anything cargo related caused the plane to diverge.
Cox gave his condolences to the victim's families because they very well may never find out what happened to the plane.
"It's a mystery unlike any in the history of aviation."