Is leaving airway at 90 degrees still a radio failure procedure? and a 360 an attention getter? after that things must have got more seriously wrong.
I don't think this turn was an attention getter. Remember no distress call was made which sounds very much like something went seriously wrong very quickly with no spare thinking capacity with nice 90 degree turns with consideration for others in the airway
Something either made the aircraft go into a violent left turn with attempts to gain control I keep thinking of the earlier Airbus rudder/tail damage
Some aircraft will bank as part of an emergency decent but not sure what the procedure is in the A320 and still you would not bank to a 90 degree turn
There is still the possibility of so many things its all guesswork even to a cargo fire or explosion interfering with control
They need the blackbox is that 15000 feet down or in shallower water ?