US airline United is to stop flights between Belfast and New York, months after a £9m rescue deal.
Two thirds of the money, which was to be given to United over three years, was to come from the Northern Ireland Executive.
The flight is the only direct air link between Northern Ireland and the US.
The European Commission has said EU rules do not allow public authorities to grant a specific airline an "undue advantage".
Reaction to loss of New York flights
The financial assistance was revealed by BBC News NI in August. However, it is understood only part of the £9m aid was ever paid to United and it has now been refunded.
On Friday, United said the last departure from Belfast will be on 9 January.
United said it had taken the decision because of the route's poor financial performance.
"We will contact customers with bookings for flights beyond those dates to provide refunds and re-accommodate where possible. We apologise for any inconvenience caused," it added.
Analysis: Julian O'Neill BBC News NI Business Correspondent
United's decision to axe its service between Belfast and New York is a setback for the airport and the Northern Ireland Executive.
But before now each had been mindful Europe could scupper a hastily arranged £9m rescue deal.
However, the gamble was considered worth taking, as without it United would have pulled out earlier.
Only part of the aid money has been paid and it has now been refunded.
Northern Ireland has long struggled to attract airlines on long-haul routes, while Dublin Airport rapidly expands its destination choices.
United's decision will not make the job any easier and, at the very least, is an undoubted knock to the prestige of Northern Ireland Plc.
Belfast International Airport said the flight is going because the European Commission blocked the funding package on state aid grounds.
The airport's managing director Graham Keddie tweeted that he was "absolutely spitting" about the decision which he blamed on "useless, faceless EU bureaucrats".