The aircraft arrived in Clare shortly after 2pm on Monday.
A US-bound transatlantic flight was redirected to Shannon Airport following the discovery of a note relating to an apparent bomb threat.
United Airlines flight UA-971 was travelling from Rome to Chicago when it was diverted to the Clare amenity. It's understood that 214 passengers and crew were on board at the time.
An emergency was declared at around 12.45pm by crew members informing air traffic controllers that they wished to divert in Shannon.
The Boeing 767-300 jet was about 200 kilometres west of County Clare when the plane was redirected back. It landed at 2.15pm following a discovery of a suspicious message.
According to Gardaí, passengers have disembarked the aircraft and are in the process of being searched. They also confirmed that each individual's luggage is set to be thoroughly investigated, as well as the plane itself.
It's also understood that each passenger's handwriting will also be checked.
A number of ambulances and Garda squad cars attended the scene. Several units of Ennis fire service were also mobilised.
According to the American Airline's website, the flight was cancelled due to “security screening disruptions."
