A passenger jet flying from Stansted airport to Poland was forced to make an emergency landing when its cabin failed to pressurize properly, according to a report.
262 passengers and nine crew were onboard the Titan Air Boeing 767 chartered flight from Stansted to Rzeszow Airport in south east Poland in March 2017.
The plane had just started to cruise at a high altitude when alarms began to go off. The passenger oxygen masks came down and the pilot bought the twin-engine plane down by 30,000 feet and diverted to land at Amsterdam's Schiphol Airport.
The Air Accidents Investigation Branch found a faulty pressure relief valve meant the aircraft had not pressurized correctly after take off.
A prior test flight had shown no problems and examination of the part after the incident discovered "no obvious reason for the malfunction".
It said the crew's quick reaction meant the plane landed safely in Amsterdam.
The report concluded: "The failure of the cabin to pressurise correctly resulted from a faulty PPRV which was installed during recent maintenance. "The maintenance checks of the replacement valves did not identify the defect with the fault PPRV. The event was a failure to pressurise correctly, rather than a sudden depressurisation and the crew's timely actions in identifying the problem and carrying out the appropriate emergency procedures ensured a safe outcome."