The flights to New York and Boston, as well as London Heathrow, which are currently operated by Aer Lingus could be axed if the airline decides to shift the services to the UK, according to The Irish Times.
The company's two Airbus A321 long-range aircraft have been grounded at Shannon since March due to restrictions on international travel caused by the pandemic.
Six UK airports, including Edinburgh and Manchester, are believed to be interested in the two aircraft.
It is reported that if a deal is made any service would be likely to begin in 2021 and run for an initial three years.
The loss of the US flights would be a devastating blow for the western airport, leaving Shannon with just one service to America.
American Airlines would be the last remaining transatlantic service provider if Aer Lingus were to pull out of Shannon, following the confirmation of Delta and United Airlines that they would not be resuming their flights from Shannon in 2021.
Prior to this, Aer Lingus told the Government that it may have to cut up to 500 jobs, from a total of 4,500, as it deals with the ongoing impact of Covid-19 travel restrictions.
Responding to the potential relocation of Aer Lingus services, Ennis Chamber, which aims to promote business in the Co Clare town and the surrounding areas, says it is "deeply concerned" with the impact it would have on the airport and the area it serves.
Ennis Chamber CEO Margaret O'Brien says a lot of foreign-direct investment is based in the region due to its connectivity.
"Over 40 per cent of US foreign direct investment in Ireland is located within the Shannon Airport catchment area and that is possibly a figure that not many people are familiar with, but it's such a large percentage of our FDI in Ireland and that accounts for over 20,000 jobs in the region."
