ACARS, Disabled or Switched off
Bilby, Desparing Traveller et al,
ACARS "was deliberately turned off" was reported early on. Now ACARS 'logs on' and 'logs off' usually on aircraft systems power up and power down. ACARS using VHF often (regularly) loses contact as the aircraft flies out of line-of-sight. There is a difference to the system between just not getting any more transmissions and receiving a log-off. So it would be possible to know if the system was shut down via a pilot input or just 'stopped' as it would if out of line of sight of VHF, fire had burned through the power supply, or the pilot had tripped a circuit breaker.
The repeated statements that someone had "switched ACARS off" rather than we received no more ACARS transmissions after the last one at cruise, implies that there is evidence of a tidy log-off. This evidence is crucial as it would settle several hypotheses - a pilot with a cockpit fire or some other emergency, does not find the correct place to log off from ACARS. SITA/ARINC should have that evidence and it should have been in the initial report.