The aircraft arrived in Clare shortly after 2pm on Monday..
A spokesperson for Garda, the local police force, told Independent.ie that the flight was diverted to Shannon, in midwest Ireland, following "the discovery of a note relating to a bomb threat on board".
A United Airlines flight over the Atlantic has turned back and landed in Ireland because of what the airline called a "potential security concern".
It's understood that 214 passengers and crew were on board at the time.
United Airlines flight UA-971 was diverted to Shannon Airport in the west of Ireland after the message was discovered en route to Chicago from Rome.
A source familiar with the matter said a written bomb threat was found onboard the aircraft, which was carrying 107 passengers, eight flight attendants and three pilots.
They also confirmed that the plane and all the passengers are now being searched. Additional units of the fire service from Ennis were also mobilised to a holding point adjacent to the M18 motorway.
United Airlines has canceled the final leg of the trip to Chicago and is working to find flights to Chicago for its stranded passengers.