Passengers on long-haul British Airways flights out of Heathrow Airport are without meals in a dispute between an airline catering firm and its workers.
Long-haul flight passengers are being offered food vouchers
BA said it can only offer tea, coffee, and water on the flights after at least 500 Gate Gourmet workers were sacked in the dispute over working practices.
The company claims it took action after an unofficial strike.
But the Transport and General Workers' Union claims the firm planned the sackings and had refused to negotiate.
A Gate Gourmet spokesperson said the company had been trying to restructure working practices and those sacked had put the jobs of the firm's 2,000 workers at Heathrow under threat.
It also said the firm has not made a profit for five years and will lose £25m this year without restructuring.
Gate Gourmet managing director Eric Born said: "After months of trying to find a consensual deal with the TGWU and the staff to resolve the financial crisis and secure the future of the company, this un-balloted action is a devastating blow."
"These actions not only jeopardise the livelihoods of our entire workforce at Heathrow, but also the services of major airlines and their customers."
He said management has met with the unions on many occasions to reach agreement on a consensual restructuring deal.
He also said the workers took strike action in response to the arrival of 130 seasonal workers which the company employs every summer to meet high demand during peak season.
But the TGWU said the hiring of the seasonal workers was a "provocative move".
A TGWU spokesperson said it was the first time such extra staff had been taken on by Gate Gourmet while permanent workers were under threat of redundancy.
After the announcement of the hiring of the seasonal workers, many of the sacked workers staged a sit-in in a canteen at the airport.
TGWU officers said the company had planned all its moves by having the sacking letters prepared in advance, hiring an outside company and alerting the police.
BA is offering affected passengers meal and refreshment vouchers at the airport and has also offered customers a refund or a chance to rebook flights.
A handful of British Airways short-haul flights are also affected.
Gate Gourmet said talks aimed at resolving the row over working practices were due to start on Friday.