The ongoing saga of the Norwegian Air application for a permit to fly low-cost routes to the US is causing friction between regulators on both sides of the Atlantic.
The US is in breach of EU-US air transport agreement by continually holding up the application, EU regulators said.
Norwegian Air, already flies to the US on a temporary license registered in Norway, and has applied for a foreign carrier permit for its Irish subsidiary.
Norwegian’s application has been strongly criticized by Delta, American, United and airline unions, saying it plans to circumvent strict labor laws and working standards.
"The European Commission considers that there is a breach of the EU-US air transport agreement by the US authorities as they are taking too long to process the application," the EU executive said in a statement.
It said other less contentious applications had been granted without delay.
The 2007 open-skies reciprocal agreement allows EU-registered airlines to fly to the US from anywhere in Europe.
Last week Norwegian Air CEO Bjorn Kjos called the hold-up "purely political" and urged a final decision as quickly as possible.
EU and US officials met November 25 and a further meeting is planned in January.