DALLAS — Norwegian Air Shuttle is celebrating a victory in its bid to expand flying between the United States and Europe.

The U.S. Department of Transportation gave preliminary approval Friday for service to the U.S. by Norwegian’s Ireland-based subsidiary.

The Transportation Department says it will take public comments before issuing a final order that could allow the subsidiary to begin flying to the U.S.

The decision is a setback for the major U.S. airlines and their labour unions, who say that the Irish subsidiary will be an unfair, low-wage competitor on key trans-Atlantic routes.