Danish workers surrounded Ryanair's first flight from Copenhagen to Dublin on Wednesday and delayed its departure by three hours in a protest over employment terms.
The dispute has been rumbling since Ryanair announced new Copenhagen routes in October to Dublin, London, Warsaw and Milan, operated under Irish employment rules. Trade unions argue their workers should be treated under Danish employment rules, generous by most European standards.
Passengers were prevented from boarding the flight by protesters waving Danish flags, who defied police calls to allow the Boeing 737 to leave.
In a statement, Ryanair called on Danish authorities "to take all necessary action to prevent any repeat of this unlawful blockade," which it said was carried out by "non-Ryanair individuals".