AIR accident officials have published their findings into a serious incident that forced a trans-Atlantic flight to make an emergency landing at Prestwick Airport.
The probe by the Air Accident Investigation Branch (AAIB) was launched after an incident involving a flight from Edinburgh to New York on February, 10, 2023.
The Delta Airlines flight, to John F. Kennedy International Airport, had to divert shortly after take-off and landed at Prestwick just after 11.30am.
One passenger captured footage of flames coming from the Boeing 767's right-hand wing, which the AAIB now says was caused by a mechanical issue.
No injuries were reported as a result of the incident, which was tackled by Prestwick's own fire crews after the plane touched down.
The AAIB have revealed that during take-off, a high-pressure turbine blade fractured in the engine on the plane's right wing, which in turn damaged five further blades.
Their report found that the fracture was the result of 'fatigue cracking', initiated by a possible combination of "hot corrosion and pitting from external contamination".
The investigators' report said: "The engine was still capable of producing thrust.
"The out of balance turbine caused vibrations sufficient to cause a slat track housing drain tube to fracture in the wing, which allowed fuel to escape from the right wing fuel tank.
"Due to the high engine vibration, the flight crew diverted the aircraft to Prestwick Airport.
"During the diversion, fuel escaping from the wing was ignited by the hot engine exhaust.
"This was recorded on video by a passenger, but the flames extinguished before the landing.
"The aircraft landed promptly, with full emergency service attendance.
"After the aircraft arrived on stand, the airport fire service noticed the fuel coming from the right wing and put provisions in place to capture the fuel, preventing it igniting on the hot engine or brakes.
"The passengers were rapidly disembarked, with no injuries."
The report reveals that the pilot in command initially intended to return to Edinburgh, telling air traffic control that "we don't have an emergency at this time, we just have a maintenance problem".
The plane's relief pilot walked to the back of the cabin "without noticing anything obviously abnormal, but on his return, the commander explained they were diverting anyway, and said: "I don't want to stay in the air with that engine."
A passenger took video footage of what appeared to be flames coming from underneath the right wing while the plane was around 21 miles from Prestwick.
But by the time a member of the cabin crew reported the possible flames to the purser, they had disappeared.
After landing at Prestwick, the report says, the relief pilot stated: "There's fuel pouring out of the wing."
The airport fire service confirmed this, telling the co-pilot: "You have fuel leaking behind the engine on the starboard wing."
The plane landed at Prestwick at 11.31am and was shut down at 11.44am.
It took approximately five minutes and 20 seconds for all passengers to vacate the aircraft.
Following this incident, a safety recommendation has been made to the Federal Aviation Administration.
It recommends that the FAA require the Boeing Aircraft Company to demonstrate that the design of the slat track housing drain tube continues to comply with the certification requirements for large transport aircraft.
The report adds: "As a result of the vibration-driven fatigue fracture of the drain tube, the aircraft manufacturer has launched a project to identify potential reliability improvements to the design, while the Federal Aviation Administration reviews the manufacturer’s finding that the risk of a catastrophic outcome from a failed drain tube is not elevated."
