Re: The investigation should center on...
BBC report says that they didn't "just turn off" - the pilots put them into "flight idle mode" and then, without the config, were unable to take them out of it.
"Airbus has already confirmed that its pilots had tried switching the malfunctioning engines into "flight idle" mode - their lowest power setting - in an attempt to tackle the problem.
Without the parameter files, the engines would have been left stuck in this mode.
This is because the planes were deliberately designed to prevent out-of-control engines powering back up, to avoid them causing other problems."