The airline said it would operate “a limited number of aircraft” starting at 8 p.m. London time.

But it warned that the disruption caused by more than 500 canceled flights at one of the world’s busiest airports would continue for many hours.

“We face a complex logistical challenge with at least 100 aircraft and 1,000 flying crew out of position,” said BA’s customer services director, Mike Street. “As a result it will take some time to return to a normal flying program.”

About 1,000 baggage handlers and other ground staff walked out Thursday in support of workers fired by catering firm Gate Gourmet. Analysts warned the airline faced losses of tens of millions of dollars.

BA baggage handlers and loaders represented by the same union as the catering staff - the Transport and General Workers Union - stopped work in sympathy with their colleagues.

Some Gate Gourmet staff were astounded at the scale of disruption.

“I didn’t expect the BA staff to join us, but we are very happy about it,” said Gary Mullins, 37, a loader for the company.

“We don’t wish to cause them any more (aggravation) than we have to,” he said of the passengers. “But it’s something that has to be done.”

Gate Gourmet, which is undertaking restructuring amid financial losses, said it was trying to resolve the dispute.

The caterer, which is owned by the Fort Worth, Texas, buyout firm Texas Pacific Group, reported a loss of $41.25 million last financial year, and was expecting a $44.84 million loss for the current year.