but still, the question what brought the plane down. if it was a deliberate act, what was the motive. there's been no claim of terrorism by the cia. fbi computer experts found no evidence of wrongdoing on the pilot and first officer's computers. malaysian sources say the plane may have deliberately dropped to a low altitude. attempting to avoid radar. that low altitude could be one of the biggest indications flight 370 was not having mechanical trouble and trying to avoid other christie for safety reasons. >> did you hear anybody say that there was any emergency call? why would you turn off a transponder? >> reporter: u.s. officials still theorize that someone deliberately steered flight 370 away from land and interest the indian ocean. still leaving the very vital questions who and why.