Middle Eastern carrier Emirates has been refused permission by the UK Supreme Court to appeal against a ruling on delay compensation for passengers who missed connecting flights.
The UK Civil Aviation Authority has urged the Dubai-based carrier to pay compensation following the decision.
Emirates had been among five airlines pursued by the CAA after denying compensation to passengers over the delays.
The airlines had been fighting claims centred on passengers' being delayed on arrival at their destination because late inbound flights to a connecting hub led to a missed connection.
All five carriers – which also include Etihad Airways, Turkish Airlines, Singapore Airlines and American Airlines – had told the CAA that they did not pay compensation in such cases.
Emirates had notably lost appeals last year over connecting flights from Manchester, via Dubai, to Bangkok and Sydney.
Although the sectors from Dubai were outside the European Union, the European Court of Justice ruled that the entire flight from Manchester, and the delay on arriving at the final destination, should be considered.
The CAA had estimated that more than 200,000 passengers annually on the five airlines could potentially be "at risk" of missing onward connections and being delayed by more than 3h at their final destination.
Since the Court of Justice had already given a "clear answer" on the matter, says the CAA, the UK Supreme Court has refused Emirates permission to appeal. The CAA says it will "progress" its enforcement action against Emirates, adding that the Supreme Court's refusal confirms the regulator's interpretation of European Union compensation law.