The quote reads: “There is no habitation of human beings in this world so fine in its way as this, the capital of Scotland.”
Other banners include quotes from Alan Rickman and Charlotte Brontë.
The error was spotted by an eagle-eyed traveller, who later posted their findings on Reddit.
“Why have Edinburgh Airport spelt his name like an American,” the user jokingly asked.
One commentor on the now-deleted post said: “Mistakes happen but you’d hope someone would have noticed this before it was up on the wall for everyone to see.”
Another added: “Sign writers make gaffs all the time, which is deplorable.”
Born in Dunfermline in 1835, Carnegie was a leading figure in the development of the American steel industry in the late-19th century
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He moved to the United States in 1848, but never forgot the people of Scotland, donating thousands to fund libraries and other community buildings across the nation, including in Edinburgh, where he built a $250,000 free library.
Responding to the spelling faux pas, a spokesperson for Edinburgh Airport said:
“Teams are already looking to replace this, and we thank passengers for their feedback to allow us to correct.”