On 8 March 2014, Malaysia Airlines flight MH370 left Kuala Lumpur for Beijing and never landed.
Since then, the most expensive underwater search in history has failed to find it, and authorities are no closer to figuring out why, 40 minutes into what should have been a six hour flight, MH370 diverted and flew towards the southern Indian Ocean with 239 people on board.
Theories abound about why the plane disappeared, and where it can be found. Some have changed, some have been discredited, and new theories have emerged, as search after search has failed to end one of aviation’s greatest mysteries.
2014: A northern landing
In the immediate, confused aftermath, an early theory suggested MH370 had been taken, not south into the sea, but north into central Asia.
This (now-discredited) theory initially had some basis in fact, based on the different ways in which MH370 was tracked.
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MH370 first “disappeared” when it turned off its transponder, causing it to vanish from civilian flight tracking after 40 minutes of flying. However, investigators could still track it using military radar, which gives a precise, physical location.
Through radar, we know MH370 started on a north-east route to Beijing, then turned and flew south-west, and then turned again, heading north-west, up towards India. But then radar coverage cut out.
After that, investigators had to use satellite data for the rest of MH370’s journey. Satellite data cannot pinpoint a plane’s position, but places it in a range that forms a circle, with the satellite at the centre. The satellite data showed MH370 was travelling further and further away from the satellite – but it was unknown whether it was moving south towards the sea near Australia (which required another turn), or was moving north and inland into Asia.
However, this northern landing idea was debunked by the company that owned the satellite, Inmarsat, and further refuted in 2015 by the discovery of debris off the coast of Africa.
2015: A ‘mass hypoxia event’ and a crash near Western Australia
In 2015, debris confirmed to be from MH370 washed up on a series of beaches across east Africa.
Not only did this confirm the plane was not intact, but modelling of ocean currents concluded that MH370 crashed in the southern Indian Ocean near Western Australia, and ocean currents then transported debris to Africa a year later.
MH370 could not have crashed in Africa, investigators said, because the satellite data was consistent only with a journey south-east into the southern Indian Ocean.