The missing Malaysia Airlines jet may have dropped to altitudes as low as 5,000 feet to avoid radar detection, according to investigators quoted in a Malaysian newspaper on Monday.
"The person who had control over the aircraft has a solid knowledge of avionics and navigation, and left a clean track. It passed low over Kelantan, that was true," the unnamed officials told the New Straits Times, referring to a state in Malaysia. "It's possible that the aircraft had hugged the terrain in some areas that are mountainous to avoid radar detection."
The technique known as terrain masking was developed by military pilots to fly towards their targets stealthily. By flying close to the ground pilots can avoid radar radio waves.
A source with Malaysia's Civil Aviation disputed this report, telling NBC News on Monday that the story was "unverified and not true."