Gardai are investigating an incident on an Aer Lingus flight bound for Boston on Wednesday afternoon.
The plane was forced to return to the airport two hours into its journey as a result of the incident which is understood to have involved a man in his 50s.
He was subsequently taken from the flight and brought to a nearby hospital where he is currently receiving medical attention.
The Aer Lingus flight had taken off from Shannon at 2.41pm and returned shortly after 5pm.
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Garda confirmed that an incident had taken place and an investigation was ongoing.
The flight restarted its journey across the Atlantic shortly after 7pm. A spokeswoman for the airport said she could add no further information while Aer Lingus have also been contacted for a comment by The Irish Times.
More details to follow