A flight from London to Philadelphia was diverted to Dublin after reporting a "chemical spill" on board.
American Airlines reported that two crew members and one passenger went to the hospital "for evaluation" after flight AA729 from Heathrow landed at 1.15 pm GMT on Monday.
Airbus A330-300 landed due to an odor "caused by a cleaning solution poured into the galley," he added.
A passenger wrote on Twitter that the spill "led to the outbreak of the disease and an emergency landing".
Another passenger wrote that he and dozens of others had been left "standing" at Dublin Airport.
A spokeswoman for Dublin Airport stated that the flight was hijacked "for a medical emergency".
"According to standard operating procedures, the emergency fire services of Dublin Airport have been completely transformed," he added.
A second American Airlines flight was encountered by emergency vehicles after it was also diverted to Dublin on Monday.
The airline reported that flight 787, from Paris to Charlotte, North Carolina, was diverted after a passenger fell ill.
The passenger was taken from the plane for treatment and the flight should start on Monday, a spokeswoman added.
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