Nok Airlines has defended the hour-long evacuation of passengers from the plane that crashed off the runway at Chiang Rai on Saturday night, saying it was following safety procedures.

Nok Airlines Plc gave the explanation in response to complaints by passengers that most of them had been kept inside the stuffy aircraft cabin for over an hour, told only that they were waiting for buses.

The Don Mueang-Chiang Rai flight with 164 passengers and six crew slid off the runway and its undercarriage collapsed as it landed in heavy rain at Mae Fah Luang international airport about 9.06pm. 

Passengers said the captain turned off the engines, leaving the passenger cabin in darkness and without airconditioning. They had been left in stuffy conditions for over an hour before being evacuated.

In the statement, Nok Air said the airline had followed maximum safety procedures by taking into consideration the passengers and coordinating with a work unit about evacuating them via a slide from the front door, as a stairway could not be placed properly against the aircraft because of the heavy rain and wet ground.

Moreover, there might also have been animals around which could have posed a danger to the passengers.

Therefore, the passengers were told to wait until their safety was assured, the statement said.