ABC News reports that two data systems were switched off with an interval of 14 minutes.
First at 1:07 AM the data transmission system was not sending data anymore, then at 1.21 AM the transponder did not sent any data.
ABC suggest this was done deliberatley.
The 'ping data' to satellites is the only system which cannot be shutdown manually.
Malaysia Airline Search Intensifies in Two Widely Separated Areas - ABC News