Authorities involved in the search for the missing Malaysia Airlines Flight 370 have mostly dismissed the theory its pilot went rogue and crashed the plane in the Indian Ocean, the Australian newspaper reported Sunday. The flight disappeared from radar en route to Beijing from Kuala Lumpur in March 2014, and an international search team has been looking for evidence about what happened to it ever since.

“The limited evidence available for MH370 was compared with three accident classes: an in-flight upset, an unresponsive crew/hypoxia event, and a glide event [generally characterized by a pilot-controlled glide],” according to Dan O’Malley, an Australian Transport Safety Bureau representative cited by the Australian. The leading theory held by investigators is that a dip in oxygen in the cabin caused the crew to lose both consciousness and control of the plane in a so-called hypoxia event.

The first clue as to what may have happened to the Malaysia Airlines craft surfaced more than a year after its disappearance. A flaperon later confirmed as a piece of Flight 370 washed up on Reunion Island, a French territory in the Indian Ocean, evidence supporting the theory the plane crashed.

Since the flaperon was found, probers have not been able to put together exactly what happened to the plane. And most authorities agree they will not fully understand what happened to it until the black box, or flight data recorder, is recovered from the cockpit, a possibility that becomes increasingly unlikely as time goes by.

Friends and relatives of the missing passengers and crew members have grown desperate about finding out what occurred as nearly two years have passed since the plane disappeared from radar. “The pilot suicide theory for Flight MH370 gained traction because, throughout the last year, there’s been no evidence of an outside plot,” aviation writer Sylvia Spruck Wrigley told BBC News last spring.