British Airways lost a U.K. court bid to halt a pilot strike at the height of the summer travel season.

London’s High Court declined to grant an injunction against a pilots’ union Tuesday, in a boost to cockpit crew who this week backed action including a walkout with a 93% majority.

Judge Elisabeth Laing gave the airline permission to appeal her decision, and a lawyer for the union said pilots wouldn’t take any further steps until after the next hearing.

It would be the airline’s first pilot strike in about four decades and may cost the airline—part of International Consolidated Airlines Group SA—as much as $50 million per day, it said in its filings for the case.

The airline and the British Airline Pilots Association are locked in a labor dispute over pay, profit sharing, and a share-awards program. It involves pilots at London’s Heathrow and Gatwick airports.