Arlene Foster has said she regrets Brussels bureaucracy prevented the rescue of the direct air link between Belfast and New York.
Two-thirds of a £9 million package for United Airlines over three years was to come from the Stormont Executive.
The European Commission said EU rules do not allow public authorities to grant a specific airline undue advantage.
The flight from Belfast International Airport to Newark in New Jersey is the only direct air link between Northern Ireland and the US.
The First Minister said: "I think it was worth doing, I think it was the right thing to do at the time, but unfortunately the EU did not agree with us.
"They have decided that we cannot proceed with what they call state aid and because of that United quickly took the decision, paid back any money that they had already received and they are now going to be leaving Belfast International Airport at the beginning of January."
She said it was a very important link into North America.
"It was the right thing to do. Of course, if we had not been in the EU, we would have been able to do it and that is the fundamental nub of this.
"I think if I were to look for a very practical expression of state aid bureaucracy, here it is."
Economy Minister Simon Hamilton agreed that the proposed spending was justified: "It was in my view a good use of public money because of the importance of that route."