Missing airline
However, all we know is that they ceased to transmit, apparently about the same time. It is unjustified to assume a deliberate act. They might both have failed due to some electrical issues.
The aircraft ending up in the southern Indian Ocean, apparently when it ran out of fuel, indicates that it was not under human control, as does the fact it was heading towards Antarctica. One reason could be that the pilots were either incapacitated or dead. None of this will be known for certain until someone finds the flight recorder.
Steuart Campbell