Cellphone video shows the entire cabin of the Airbus violently shaking from side to side.
One witness described the plane was shuddering like a washing machine.
The flight, carrying 350 passengers, departed Perth, Australia, and was en route to Malaysia's capital. It was supposed to be a nearly six-hour flight, but 90 minutes into the trip, the pilot was forced to turn back around.
The captain of the plane issued a dire warning: "Also please, listen to everything. Our survival depends on your cooperating. Hopefully, everything will turn out for the best."
"Lots of people (were) crying," one passenger said. "Lots of people (were) pulling out the life jackets and stuff, pretty much preparing for that sort of thing. We thought there was a good chance that we were going down."
But somehow two passengers, Mitch and Damos, managed to make light of the ordeal, taking video of themselves shaking on the flight.
The pilot was finally able to land the plane back safely in Perth.