MH370 disappeared on March 8, 2014 en route from Kuala Lumpur to Beijing with 239 people on board. The plane lost contact with civilian air traffic control at 17:21 UTC, but could still be seen by military primary radar until 18:22 UTC. However, after an initial diversion MH370 passed mostly along the boundaries between flight information regions (FIRs) – aerial territories under the jurisdiction of different air traffic controllers.
When the plane disappeared from secondary radar near a waypoint called IGARI it was on the boundary between Singapore and Ho Chi Minh FIRs.
It then turned around and flew along the border between Kuala Lumpur and Bangkok FIR.
According to 2015 book ‘The Plane That Wasn’t There’ MH370 was picked up by both Thai and Malaysian military radar, but both ignored it thinking the other would respond.
RAF navigator Steve Pierson told author Jeff Wise: “That’s quite clever.
“Because if you fly down the FIR boundary the controller on each side might assume the other was controlling you.
“Usually a civilian air traffic controller would call his counterpart to check – military, not so much.
“They might think: ‘Oh, that must be the other country’s aircraft, that’s not my problem, I won’t worry about it.’
“And the other country thinks: ‘Oh, that’s their problem, I won’t worry about it.’”
The evidence collected by Mr Wise suggests that, in this way, MH370’s hijackers used the boundary to fool the air traffic controllers into inaction.
Neither side tried to find out what the aircraft was doing or why.
Mr Wise said: “Not until it was practically on top of the Malaysian Air Force base at Butterworth did the plane break into the middle of Malaysian airspace and dash out of radar range.
“If MH370 was being steered in such a way as to avoid detection, the plan worked.
“Both Malaysia and Thai military radars apparently picked up the plane but no humans noticed until the radar recordings were inspected the following day, by which point the plane was long gone.”
Mr Pierson also pointed out that flying precisely along the boundaries between military airspace implies the hijackers knew “exactly what they were doing” and possibly had military experience.
However, there are many theories as to what happened to MH370 and where it may be located.
Some believe it was hijacked by terrorists and others believe the pilot may have absconded with the plane, as well as numerous other theories.
The official investigation concluded it must be in the southern Indian Ocean, but others have also disputed this claim.