IN YET another case of Chinese passengers opening emergency exit doors on flights, a Chinese man did the deed on a China Southern Airlines flight before take-off from Nanjing Airport on Monday, reported the local media.

His actions, committed immediately after he had boarded the Nanning-bound flight, shocked flight attendants as well as other passengers who were in the process of boarding the Boeing 737-800, according to The Beijing News.

Giving no explanation for what he had done, the unidentified man then sat by the open door, staring outside.

Nobody had tried to stop him, and he was able to open the door easily, said eyewitnesses quoted by The South China Morning Post (SCMP). Flight attendants were busy helping other passengers.

When asked why he had opened the door, he was quoted by SCMP as replying: "This door is not important."

The airline said he did not seem to show any indication that he knew he had done something wrong, the SCMP reported.

The man's actions caused the flight to be delayed by almost one hour, said SCMP, adding that it finally took off safely after exhaustive security checks.

The Beijing News reported that the man would spend the Chinese New Year holidays in prison, after the police detained him at Nanjing Airport.

The police said they would hold him for 10 days, SCMP reported.

There have been other similar cases of Chinese passengers opening the emergency exits of planes.

Last month, 25 Chinese passengers opened the emergency exit doors on a plane before take-off in a show of anger after their flight was delayed, Agence France-Presse reported.

On Dec 12, last year, a Chinese passenger on a China Eastern flight caused a two-hour delay when he attempted to get off the plane faster by using the emergency exit.

Also in last December, a Chinese man opened the emergency exit of a Xiamen Air plane just before take-off. The first-time traveller reportedly wanted to get some fresh air.