A flight from Dublin Airport to Los Angeles International Airport had to make an emergency landing in Shannon after systems showed one of the engines was on fire.
The Air Accident Investigations Unit has issued a report saying no fire had actually found and that the probably cause for the warning was fatigue failure.
The flight took off from Dublin Airport on December 28 before making an emergency landing in Shannon after warnings flashed 15 seconds after take off.
The report outlined how the crew were informed the right hand engine had gone on fire - but that the warning stopped once they shutdown the engine.
A MAYDAY was declared and a gadget that discharges a fire extinguisher into the engine was triggered.
The crew then landed in Shannon Airport where it was established that there was no apparent damage and the warning had been caused by "hot, high pressure bleed hair escaping" into the engine.
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A later more detailed investigation found the fire warning was caused by a fractured component in the aircraft's bleed air outlet.
The report said: "The ENG 2 FIRE warning was subsequently found to have been caused by hot, high pressure bleed air escaping into the No. 2 engine compartment as a result of the fatigue failure of a short section of No. 2 engine’s high pressure bleed air ducting."
Despite no fire, Dublin's Air Traffic Control said smoke had been seen coming from the plane from the left site despite the fault warnings showing problems on the right.
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A detailed investigation into the incident concluded that no new safety recommendations were needed.
The report found that the " airworthiness certification for the aircraft was valid" and that the flight crew acted as required.
