Asiana Airlines has banned the sale of certain emergency exit row seats following an incident in which a passenger partially opened an emergency exit door during a flight.

The man was able to partly open the door of the A321-200 aircraft on Friday, May 26, as it came in to land near Seoul.

Fellow passengers on board the Airbus A321 aircraft tried to stop the person but he was able to partly open it, which allowed cold air to rush through the cabin.

In response, the airline announced it would no longer sell 32A and 26A on its A321-200 aircraft.

“As a safety precaution, this measure will apply even if the flights are full,” it told AFP news agency on Sunday.

This wouldn’t necessarily stop other passengers from trying to open the emergency door but could mitigate the risk, as the incident was largely possible due to timing.

That the passenger could be seated, in preparation for landing, and able to easily access the door, likely made the act possible, according to aviation experts.

News of the act prompted many people to ask how a passenger was able to open an emergency door while the plane was in the air.

It all lies in the timing.

An Asiana official said the passenger opened the door approximately three minutes before landing when the plane was at an altitude of 213m.

Cabin pressure means an aircraft door is typically impossible to open mid-flight. The force created by a difference in pressure outside and inside the aircraft equates to thousands of pounds, so a person could not open it.

However, at 213m, there would not be a significant difference in pressure, making it possible to open.

The mechanics of the emergency door may have also made things a little easier. Unlike a car door, which opens out, the A321′s door slides open parallel to the body of the plane, similar to a delivery van door. This makes it easier to open against the force of the wind.