It’s been more than four years since Malaysia Airlines Flight 370 vanished without a trace, and authorities have yet to provide an official explanation for the aircraft’s disappearance. Though some have theorized the tragedy was caused by technical malfunctions, a terrorist attack, or even extraterrestrials, a group of aviation experts are convinced the pilot crashed the plane in a carefully orchestrated murder-suicide mission.

A panel of analysts explained their theory during a recent episode of 60 Minutes Australia, suggesting Captain Zaharie Ahmad Shah deliberately went off course to avoid radar detection before flying the plane into the Indian Ocean.

The experts said they believe Shah put on an oxygen mask before he depressurized the Boeing 777, effectively rendering all 227 passengers and 11 crew members unconscious. This could explain why there were no communication attempts from the people on board, such as mayday calls or good-bye texts to family members.

The panel also pointed to the plane’s unexplained detour over Penang, Malaysia—the state where Shah was raised.

“Captain Zaharie dipped his wing to see Penang, his home town,” Simon Hardy, a senior pilot and instructor, told 60 Minutes. “If you look very carefully, you can see it’s actually a turn to the left, and then start a long turn to the right. And then another left turn. So I spent a long time thinking about what this could be, what technical reason is there for this. And, after two months, three months thinking about this, I finally got the answer: Someone was looking out the window. It might be a long emotional good-bye—or a short emotional good-bye to his home town.”

Families of the MH370 victims told CBS News they were familiar with this murder-suicide theory; however, most of them say they will not accept this explanation without forensic evidence.

Shah’s family echoed the sentiment, telling the news outlet: “pointing a finger toward [Shah] does not make them expert investigators—they have to find the plane.”