>> malaysian 370. >> the controller here speaking to ho chi minh. he says good night 370. something i would do. >> there was no indication that anything had gone wrong. >> david soucie is a former safety inspector for the faa. so for the first 40 minutes of this flight up to that point everything has been routine. >> mm-hmm, yes. >> everything was routine until now. two minutes after talking with air traffic control, 40 minutes into the flight, the plane's transponder goes dark. >> the plane's transponder is effectively the instrument that sends out a signal to air traffic control. it tells you what height it's at, which direction and what speed it's traveling. suddenly this giant 777 is blind