The Irish Travel Agents Association says the decision by Norwegian Air to end its transatlantic flights between Ireland and the US is a big blow to Cork and Shannon airports.
The airline flies six routes from Dublin, Cork and Shannon to the US and Canada.
However, the services will cease from September 15.
CEO Pat Dawson said customers could face further costs.
"It is a big blow, particularly to our smaller airports outside of Dublin," he said.
"Full refunds, which is not much use to anybody as such, will have to look at other airlines to see where they can get a space.
"At this time, people going to the States would have to book in advance, so the airfares of what they paid Norwegian and what is available now...I'd say would be vastly different."
Shannon Airport Group: Norwegian pull-out to cost region €60m
The acting CEO of the Shannon airport group, Mary Considine has said that the decision of Norwegian airlines to axe its transatlantic services will cost the region €60million.
Norwegian has confirmed it is stopping its transatlantic flights to Ireland from next month.
"It is important that a replacement service is found as quickly as possible, but it will take time," she said.
"Connectivity to the region is important and it is also important to work closely with agencies like Tourism Ireland," added Ms Considine.
The head of communications at Cork airport, Kevin Cullinane, said that the airport had fought “long and hard” to get a transatlantic service and will double their efforts to find a replacement for Norwegian.
"However, it will be 2021 at the earliest before that happens," he warned.
The airline has blamed the global ground of 737MAX aircraft for the decision.
“Since March, we have tirelessly sought to minimize the impact on our customers by hiring, so called wetleasing, replacement aircraft to operate services between North America and Ireland," said Matthew Robert Wood, one of the airline's senior vice presidents.
"However, as the return to service date for the 737 MAX remains uncertain, this solution is unsustainable."