The Unite union has lost its court appeal against British Airways' decision to reduce the number of cabin crew staff on its flights.
BA made the change in November of last year, a move that was upheld in the High Court in February following a legal challenge by Unite.
Unite subsequently went to the Court of Appeal, which has now also ruled in BA's favour.
Unite is now balloting cabin crew staff on a new BA offer to end strike action.
BA issued a statement welcoming the ruling.
The company said: "We are pleased with today's Court of Appeal judgment, confirming that the modest changes we made to onboard crew numbers on flights from Heathrow 12 months ago were reasonable, did not breach crew contracts and can remain in place."
It added that the changes had made what it called a "substantial contribution" toward easing the company's financial position.
It said its crew had accepted these working arrangements "without difficulty".
Unite has yet to comment.