MH370 vanished on March 8, 2014 en route from Kuala Lumpur to Beijing with 239 people on board. According to 2015 book ‘The Plane That Wasn’t There’, the air traffic controllers’ computers continued to display the aircraft symbol even though the plane’s ADS-B signal had “winked out” and it had disappeared from radar. MH370 had been flying towards IGARI, a waypoint that is far enough out over the ocean that it is sometimes out of range – a kind of “blind spot”.
The automatic tracking system often temporarily loses planes around IGARI for a few minutes, before they are picked up again by radar and radio.
Author and aviation expert Jeff Wise said: “You might think that all this would set off red flags for the air traffic controllers, but in fact this kind of winking out is normal.
“Air traffic controllers continued to see the plane symbol on their screens as the system assumed the plane remained on course.”
MH370 was supposed to be travelling over the boundary of Malaysian-controlled airspace to Vietnamese-controlled airspace.
When airliners do this they contact air traffic controllers on the ground informing them they are leaving the airspace, then a few minutes later radio in to the controllers in their new airspace.
MH370 contacted Kuala Lumpur and radioed out with the words: “Goodnight. Malaysian 370.”
Air traffic controllers in Hanoi saw the plane’s symbol continue as normal and waited for them to radio in.
However, they never received the expected communication from MH370.
Mr Wise added: “Not until 15 minutes had passed did air traffic controllers in Hanoi begin to wonder why MH370 hadn’t radioed in to establish contact.”
This is when they raised the alarm and began to phone round other air traffic control stations in the region trying to work out where the plane had gone.
Over the next few hours, air traffic controllers phoned each other and the airline but to no avail.
When dawn broke, MH370 was declared missing.
It was in those first crucial minutes that the system, designed to compensate for normal signal failures around waypoint IGARI, actually worked against them.
Had the plane disappeared from their screens, they may have known something was wrong sooner.