The airline Norwegian has confirmed it will be unable to operate flights to and from Cork and Shannon airports for the rest of the year.
It comes amid the ongoing grounding of Boeing 737 Max aircraft.
In a statement quoted by the Irish Independent, the airline said flights will continue to be re-routed via Dublin.
Cork to Boston Providence is a seasonal route, meaning there are only flights during the summer.
However, winter flights have also been impacted at Shannon.
A spokesperson for Shannon Group said they were disappointed for passengers.
The spokesperson said: “The world-wide grounding of the 737 Max aircraft is having a serious impact for Shannon passengers. Proportionally, no other Irish airport has such a high level of activity operated by the 737 Max aircraft. At peak this aircraft type would have operated 13 weekly flights from Shannon to North America.
"We now estimate that the loss of these flights, which include this year’s Air Canada service, will mean a loss of over 120,000 seats at Shannon in 2019 and as a result our overall passenger numbers will be down."
In a statement, Cork Airport said it was "aware of the positive impact" a Cork to US route has for tourism in the region.
It adds: "We are continuing to work with Norwegian, and other airline partners, on securing additional transatlantic routes in the future."
Aviation agencies around the world - including the Irish Aviation Authority - made the decision to ground Boeing 737 MAX models in March.
It followed two fatal accidents involving Boeing 737 MAX 8 planes.
157 people died when a Boeing 737 MAX 8 belonging to Ethiopian Airlines went down shortly after take-off from Addis Ababa on March 10th.
In October, all 189 people on board a Lion Air flight died after it crashed into the sea shortly after taking off from Jakarta in Indonesia.
Boeing says it has updated software for the 737 Max planes, and hopes to return the planes to service once testing and certification is complete.