Changes to the magnetic poles of the Earth have forced the renaming of the main Cork Airport runway.
Because of gradual changes in the Earth's magnetic poles, runways have to be designated roughly every 50 years.
In 1961, Cork Airport's main runway was designated as Runway 17/35. However, it is now Runway 16/34.
Over the past 57 years, the Earth's magnetic poles have changed and shifted the magnetic headings of the runway.
The runway now stands at 164°M and 344°M respectively.
The formal redesignation took place early yesterday morning before the first wave of departing flights.
"Cork's two-digit runway designator is crucial for pilots during take-off, landing and taxiing," explained Cork Airport operations and safety manager Con Dooney.
"Thanks to the co-ordinated efforts by Cork Airport and the Irish Aviation Authority, we are delighted to complete the renumbering overnight without any delay to our busy first wave of departing flights.
"Work on the actual repainting of the runway numbers started as soon as the final flight landed last night to be finished in time for the first departure this morning at 6am."
Cork Airport safety lead Nathan Wall said that work on the project had started two years ago and had included updating pilot charts and airport directories.
The next redesignation for Cork Airport is due in 2068.