Six passengers, including a pregnant woman, were hospitalised after a Ryanair flight from Dublin to Bristol was forced to make an emergency landing in February last year, according to a report from the State's Air Accident Investigation Unit.
Immediately after the Boeing 737 took off from Dublin on a scheduled flight to Bristol, a bang was heard in the cabin area, which was followed by a blast of hot air, and what appeared to be smoke, entering into the cabin, the AAIU reported.
The cabin staff alerted the flight crew and the captain declared an emergency before making an immediate return to Dublin airport.
He ordered an emergency evacuation, which resulted in some passengers having to climb out of the fuselage onto the wing of the aircraft. There was then confusion over how they should get down, the report noted. Some 120 passengers, two infants and five crew were on board.
Inspection of the plance found that a duct joint in the pressurisation system had failed. This allowed heated engine air to enter the cabin. The Investigation has made a total of four Safety Recommendations.
It said the age (22) of the aircraft, along with the number of flight hours and cycles were factors in the falure of the duct, which itself was caused by excessive wear of rivets.
"A possible failure to replace the bonding material during a previous repair may also have been a factor," the AAIU said.
It added that the failure of the duct "did not threaten the safety of the aircraft".
"However the manifestations of the failure in the cabin were sufficient to cause concern to the passengers and crew. This concern was the basis for the crew's decision to declare an emergency, to initiate an immediate return to Dublin Airport and to evacuate the airplane after landing."
The AAIU said the actions of the aircraft crew were "appropriate and effective".
The use of stronger fasteners (rivets) has been since recommended in servicing such aircraft.
The AAIU also suggested Ryanair should review its safety card, which explains evacuation procedures to passengers, after there was confusion about how they should get down from the aircraft wing during the emergency evacuation.
Ryanair told the AAIU it was examining how they could best respond to this safety recommendation.