The 3 pieces of evidence that point to possibility that Malaysia Airlines plane was taken over

New revelations about a missing Malaysia Airlines plane have left anguished relatives contemplating the prospect that those on board endured a terrifying, high-altitude hijack ordeal that may have lasted nearly eight hours.

But while the disclosures have led to increased speculation of a terror plot or pilot suicide, for some they offered a glimmer of hope - that the Malaysia Airlines plane carrying 239 passengers and crew may have landed safely and that, somehow, loved ones may be alive.

Three pieces of evidence that aviation safety experts say make it clear the missing Malaysia Airlines jet was taken over by someone who was knowledgeable about how the plane worked:

Transponder

One clue is that the plane’s transponder - a signal system that identifies the plane to radar - was shut off about an hour into the flight.

In order to do that, someone in the cockpit would have to turn a knob with multiple selections to the off position while pressing down at the same time, said John Goglia, a former member of the National Transportation Safety Board. That’s something a pilot would know how to do, but it could also be learned by someone who researched the plane on the internet, he said.