DENVER - A former air traffic controller told 7NEWS he is stumped about the fate of the missing Malaysian airliner.
For more than 20 years, Carmen Reale monitored aircraft in Syracuse, New York, now he serves as an instructor at Metropolitan State University in Denver.
"We have no clues, and there are always clues," said Reale.
Reale said an air traffic controller will typically monitor an aircraft's speed, altitude and location on their screen. Yet even with that system lost, other radar can often reveal if there's anything in the sky or the sea.
"We have transoceanic flights, thousands of them every day, and we don't lose planes because they go over the mandatory recording points."
Reale is intrigued by reports of the jet's fluctuating altitudes.
"The lower it is, you'll get blind spots and you can lose a plane that way," said Reale.
"And what about going really high, what does it do for coverage?" asked 7NEWS Reporter Marc Stewart.
"You know, that should actually make it easier to track," said Reale.
Some big questions still remain, including how and why the transponder was disabled.
Those who sit in the cockpit stress that first impressions are not always correct.
"You don't make any assumptions, right off the bat, even when it looks completely obvious," said Kevin Kuhlmann, a former airline pilot in Denver.
Search crews from 26 countries, including Thailand, are looking for Malaysia Airlines Flight 370, which vanished early March 8 with 239 people aboard en route from Kuala Lumpur to Beijing.
Aircraft and ships are scouring two giant arcs of territory in the remote waters of the southern Indian Ocean, according to the Associated Press.