British Airways had “no option” but to cancel almost all its flights yesterday and today due to an unprecedented walkout by pilots.

Around 200,000 passengers and 1,700 flights have been affected by the 48-hour action with a further walkout planned for September 27.

The action could cost the airline up to £40 million a day with around 4,000 pilots are involved in the strike.

Podcast: BA strikes

The strength of feeling among pilots in the dispute over pay and conditions should be a “wake-up call” for BA, according to the British Airline Pilots Association.

Balpa said the strike action was supported “virtually 100%” of its members at BA in the dispute over pay and benefits.

BA was forced to offer customers full refunds or the option to re-book to another date of travel or alternative airline.

Balpa said there are currently no further negotiations planned with the airline and the strike will continue until 11.59pm tonight.

General secretary Brian Strutton said: “Pilots are standing firm and have shown just how resolute they are.

“British Airways needs to start listening to its pilots and actually come up with ways of resolving this dispute.”

The industrial action came despite BA chief executive Alex Cruz claiming an agreement had been reached two weeks ago at the conciliation service Acas.

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“We shook hands and unfortunately the union leaders were unable to put the deal through to their representatives,” he told the BBC, indicating that it covered an 11.5% pay rise.

Cruz added that there was still “lots of opportunities” to continue discussions around multiple options around the pilots’ working conditions

BA said: “We understand the frustration and disruption Balpa’s strike action has caused. After many months of trying to resolve the pay dispute, we are extremely sorry that it has come to this.

“Unfortunately, with no detail from Balpa on which pilots would strike, we had no way of predicting how many would come to work or which aircraft they are qualified to fly, so we had no option but to cancel nearly 100% our flights.”

BA added: “We remain ready and willing to return to talks with Balpa.

“Our customer teams – supported by additional colleagues – have been working tirelessly to help as many [passengers] as possible and to provide options, including a full refund or re-booking to a different date of travel or alternative airline.”