"I need to know how anybody could interdict our systems,” as well as “this aircraft was disabled in three primary systems. To be able to disable those requires a knowledge of the system which even our pilots don’t know how to do. Somebody got on board and knew exactly what they were up to.”
How can anyone assess with such confidence what things his employees
don't know?
It is known (or at least it is to be hoped) that the pilots are thoroughly familiar with many, if not most, of the systems on board. Of course, there will be some aspects of the aircraft that pilots are not explicitly trained in; a pilot is not expected to be able to build his aircraft from scratch.
There may be ways to disable certain systems that pilots are not trained to know about, but then, nobody is born with that knowledge; it must be learned somewhere. And surely a trained and qualified 777 pilot is further along that road to knowledge than anyone else?
The implication that a terrorist or terrorists unknown, coming from outside the aviation industry, have the ability to learn such things more readily than persons who start their acquisition of knowledge from the position of type-qualified pilots is, frankly, bizarre.
If it can be done, any intelligent and motivated person can learn to do it. Complex failure modes can be the result of deliberate action - and as Backoffice points out, this may not imply malice, but can arise from a genuine attempt to prevent disaster.
Complex failure modes can also result from damage to systems; while not readily reproducible, it is nevertheless common for fires and other escalating failures to produce patterns of failure that common sense would suggest were hugely implausible.
The evidence presented so far is insufficient to rule out any of the following:
Deliberate malicious act by one or more passengers
Deliberate malicious act by one or more crew
Deliberate crew actions intended to prevent or mitigate disaster (unsuccessful)
Non-deliberate failure of one or more systems leading to fire or structural damage, resulting in an unusually complex series of events
In other words, despite the vast quantity of ink and pixels expended so far, all that is really known is that the aircraft went missing; and that there is some good evidence, including primary radar traces and the INMARSAT pings, that it re-crossed the Malay peninsula, and then headed into the southern Indian Ocean, after it disappeared from secondary radar.
Any hypothesis that fits those facts is possible; none are plausible; one is correct.