ACARS allows computers on the plane to relay technical information about its condition to computers on the ground.
However, this system was turned off on MH370.
The Malaysian prime minister added: “We can say to a high degree of certainty that the ACARS was disabled.”
This would imply that someone was in charge of the controls deliberately taking the plane off-course.
However, aviation consultant Alastair Rosenschein told Channel 5 documentary ‘Flight MH370’ that he is not so sure.
The narrator said: “One expert said using the word disabled was unfortunately misleading.”
Mr Rosenschein said: “There is no way they could know that.
“All they could know was that the transponder was switched off, they stopped receiving those signals.
“Yet, they led everybody into this mindset that it was a deliberate action.”
That said, to switch off the ACARS, an intimate understanding of the cockpit controls is needed.
This does seem to imply that someone with considerable knowledge tried to make the plane ‘go dark’.
According to the Channel 5 documentary, this fact means “mechanical failure is looking less plausible”.
Mr Rosenschein emphasised also the importance of working out exactly what happened to the missing aeroplane.
He said: “This accident may apply to other aircraft or it may have been an engineering repair job which has been done incorrectly and may also affect other makes of aircraft.
“So it is vital that one tries one’s hardest to get to the bottom of it.”