A Lufthansa spokeswoman said the man who stepped in was fully licensed to operate and fly the 747. "In such circumstances it's absolutely normal procedure for the pilot, the flight captain, to continue to operate the aircraft," she said.
"Also, where necessary, the cabin crew are fully trained and can be called upon to read checklists back to the pilot. The procedures are in place for such an eventuality. But the effort of the off-duty pilot were certainly appreciated," she added.
The Irish Aviation Authority has been notified of the incident and has received a briefing report.
The air accident investigation unit of Ireland's department of transport has been notified and is investigating. Experts from the AAIU attended the plane after it touched down in Dublin.
"Whenever you have any sort of medical issue on board, whether it's a doctor or appropriately qualified person, that's always appreciated," the spokeswoman said.
"The flight would have been operated as per procedures and safely even if the off-duty pilot had not been there," she added.
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