Four cabin crew on board an Aer Lingus flight had to be taken to hospital after the aircraft suddenly levelled off while descending towards Dublin Airport.
Details of the incident, which occurred in 2012, emerged today in a report by the Air Accident Investigation Unit.
The report recommended Aer Lingus should review its training programmes and procedures to ensure that flight crews are familiar with levelling off manoeuvres and the risks associated with manual flight control inputs during high altitude operations.
The incident occurred on 7 September 2012, when the Airbus A320 was en route from Milan to Dublin.
There were 62 passengers and six crew on board.
At around 120 nautical miles southwest of Dublin, the flight crew were instructed by London Air Traffic Control to descend to 34,000ft.
However, flight level 24,000ft was entered into the auto-pilot in error.
As the aircraft was descending, the co-pilot queried the input flight level.
Air traffic control confirmed the correct flight level.
The pilot abruptly levelled the aircraft off as it was at 34,000ft and then he told the co-pilot: "I owe you a big one there."
The pilot expressed disbelief when he was told four cabin crew were injured as a result of sudden move.
A doctor on board administered first aid to one crew who had a broken ankle.
When the plane landed, all four were taken to hospital although three were later discharged.