“After many months of trying to resolve the pay dispute, we are extremely sorry that it has come to this,” British Airways said by email on Monday.

The airline may owe disrupted passengers hundreds of pounds in compensation. Here’s what travelers need to know.

The numbers: The airline is offering salary increases totaling 11.5 percent over three years, taking the average pilot from 167,000 pounds in salary and other payments and allowances annually, or about $205,000, to more than £200,000.

The pilots say that they are asking for slightly more — and that the strike will cost the airline around £40 million a day. They plan another strike for Sept. 27.

Advance planning: British Airlines said it had contacted customers two weeks ago to offer a choice of full refunds or alternative flights, even on different airlines. It was not exactly a seamless process.