Passenger Opens Emergency Door Mid-Air on Asiana Flight, Video Shows Terror

It was as terrifying as it gets on a flight over South Korea Friday ... after a passenger opened an emergency exit door mid-flight ... triggering chaos and fear in the cabin.

An Asiana Airlines Airbus was cruising high during its 1-hour flight when a passenger somehow was able to open the emergency exit just behind the wing. Other passengers tried to thwart the effort but failed.

The plane -- which normally cruises at around 500 MPH -- became a wind tunnel inside the cabin, and the video graphically shows the force of the gusts that enveloped the 194 passengers.

The plane landed safely and the passenger who opened the door was taken into custody. The motive is unclear.

Miraculously, none of the passengers suffered any injuries -- however, some were taken to the hospital for observation.