>> if you were doing something nefarious and switching off acars would be a crucial part of making the plane go dark. >> 17 minutes after the plane went dark, 19 minutes after the last words from the cockpit, there was still no check-in with vietnam air traffic control. the call former chief pilot nik huslan has made thousands of times. >> you have to be like drunk for you to forget to check in after somebody tells you immediately to check in. every pilot would do that as soon as possible. anything after two or three minutes already abnormal. >> around 1:38 a.m., air traffic controllers try to reach the aircraft. >> they tried the radio, they tried to call and see if mh-370 was out there, no response. >> you attempt to communicate directly with the aircraft first? >> right. that's first thing you do. if that's not successful, they