Another mid-air incident in Asia, after a Malaysian airlines flight from KL to Sabah on Borneo dipped its nose and dropped suddenly.
The incident happened on Sunday, but has only come to light after passengers posted their stories on social media.
The airline says the Flight MH2664 from KLIA turned back due to "technical issues" with the aircraft.
The aircraft was an eight-year-old Boeing 737-800, the same type of aircraft that crashed in southern China last month, killing all 132 passengers and crew.
Passenger Halimah Nasoha posted about her experience some 30 minutes into the mid-afternoon flight,
saying many passengers panicked, screamed and some were crying as the aircraft lost altitude sharply.
A flight radar tracker shows the plane dropping suddenly from 7,620 to 7,000 metres, a drop of some 620 meters.
The passenger said, "It was very frightening to many of us. I really felt I was going to die.
该旅客表示：“我们很多人都觉得非常害怕 。我当时真的觉得自己要死了 。
The flight was unstable. It went up and then went down. But the first time it went downward was the worst."
飞机很不稳定 。一会儿上升，一会儿下降 。但第一次下降是最糟糕的 。”
Passengers claimed the terror lasted for about 10 minutes.
The Civil Aviation Authority of Malaysia says they'll be examining the plane's internal Flight Data Monitoring System, but indicate the pilots appear to have responded correctly.