just two minutes after that very standard conversation, at 1:21 a.m., someone in the cockpit turned off the transponders that send speed, location, altitude, and heading information. soon after that the plane turned around. at 2:15 a.m. the last radar contact in the strait of malacca headed north. over the next six hours the plane transmitted one ping an hour to an orbiting satellite until 8:11 a.m. when the last ping was received. that puts the plane somewhere along these two arcs as far north as kazakhstan, as far south as the deep indian ocean. australia is now taking over that search zone. >> we will do our duty to the families of the 230 people on that aircraft who are still absolutely devastated. >> reporter: experts say turning off acars then the transponders then flying the 777 for hours requires expertise, which is why there's intense focus on the cockpit crew. >> what is a potential motive and what can be learned from looking deeply into the