A Mayday was declared on a flight to Edinburgh due to problems with its air conditioning system.
The Air Accidents Investigation Branch (AAIB) said problems with the temperature control system had not been recorded in a paper log on board the Flybe aircraft, meaning crew members were unaware of the issue.
The heating issues saw passengers and staff being uncomfortable during a previous flight, so the commander decided to reset the air conditioning system.
He was then interrupted by trying to help resolve the catering issue – a lack of drinking water for crew members – and did not complete the procedure before take-off from Belfast.
The report says both pilots returned to their stations and were keen to depart on time, but their workload was now “significantly above the norm”.
Air conditioning had been left turned off, which led to the vessel not pressurising and the cabin altitude warning sounded shortly after reaching the cruise flight level of 10,000ft.
A Mayday was declared but the crew then noticed the air conditioning system was not operating, which they switched on and the aircraft stabilised near Glasgow.
The company wanted the flight to continue to Edinburgh and it arrived at 6.55pm on September 21 last year.
AAIB said in its report: “The effectiveness of the crew’s actions was reduced by the high workload resulting from operational factors and by their attempts to deal with the symptoms of a technical issue with the aircraft, which had not been communicated to them.”
A Flybe spokeswoman said: “We thank the AAIB for concluding its investigation and report on the incident which took place on September 21, 2018.
“Flybe can confirm that a number of actions have since been incorporated into our systems and procedures to ensure that the chances of such an event reoccurring are significantly minimised.”
The commercial flight had four crew members and 70 passengers on board.