Chestnut
^Secondly that the plane was still being flown by the airline pilot when it turned off course.^
The plane took a very unexpected turn at exactly the moment it was between two countries, so one country's air traffic control had not handed over to the second at that point. Therefore the flight could turn and skim along this 'no contact' corridor and escape detection until further south. Only the pilot could have calculated this very clever manoeuvre.
When one air traffic control centre (ATCC 1) is handing over control of an aircraft to another (ATCC 2), the procedure goes as follows. ATCC 1 contacts ATCC 2 and passes over all the details of the aircraft, such as position, height, heading, speed, and the SSR Code which highlights the aircraft on both ATCCs' radar screens. Once ATCC 2 are happy that they have identified the aircraft on their radar screens, they will inform ATCC 1 about the radio frequency on which they wish to talk to the aircraft. ATCC 1 then ask the aircraft to call ATCC 2 on that frequency. The aircraft will acknowledge the frequency to ATCC 1, and will then call ATCC 2 on that frequency. Once the aircraft is talking to ATCC 2, then control officially passes. So the aircraft is never in a 'black hole' during the handover/takeover process, and I am mystified as to why the Vietnamese ATCC did not contact their Malaysian colleagues when MH370 failed to call them on the new frequency and disappeared off radar... Or , more likely they did, but that was not covered in the TV programme's narrative, which gave the impression that the alarm was raised some time later.