CNN Erin Burnett OutFront March 13, 2014 23:03:00
Radar data. and the fuel range. it had about seven hours of fuel. flew about two hours before the turn, and then that leaves five hours. that gives you the big ring, and the combination of facts that brings us to the other realm. and this came from the malaysian air force, i'm told by people that know this well. reading radar and pings is more of an art than a science. you need to distinguish background noise and get a sense of direction. that gives them an indication that they should be looking in the direction of the indian ocean.
Source: archive.org