Geoffrey Thomas, editor in chief of AirlineRatings.com, says the flight's route was "quite benign, doesn't fly over any conflict zones."

"Nothing unusual about this flight, just unusual that it disappeared, which obviously is very worrying."

He added: "There’s a lot of conflicting information, this aircraft was some time from touchdown, hadn’t started its descent. There’s nothing very unusual other than it suddenly disappeared. It’s too early to speculate but it’s extremely unusual. It doesn’t appear to be a mechanical issue either."