Around 4,000 of BA’s pilots will walk out over Monday and Tuesday (9-10 September), grounding in excess of 1,500 flights at an expected cost of around £40 million a day to the flag carrier.

BA has advised passengers not to travel to their departure airports unless they have alternative arrangements, with the overwhelming majority of passengers having been made aware of the potential strikes weeks in advance.

Pilots union Balpa has been in dispute with BA for several months over pay, with the union claiming BA is failing to adequately reward its pilots for the role they play in delivering BA – and owner IAG’s – record profits.

IAG made around £3 billion last year, up 9%, some £2 billion of which was contributed by BA. Its pay offer, believed to be worth around 11.5% over three years, was rejected by Balpa’s BA members in July.

While both BA and Balpa say they are ready to return to talks, both claim obstinance on the other’s part.

BA says Balpa is refusing to agree to talks without preconditions, while Balpa says BA repeatedly refused to reconvene at government conciliation service Acas late last week.

Balpa has another 24-hour walkout scheduled for 27 September.

Most of BA’s UK flights on Monday and Tuesday have been cancelled. There were a number of cancellations on Sunday to allow BA to reposition aircraft and crew, and there are expected to be knock-on effects on Wednesday (11 September) as well as a result of Balpa’s action. Further cancellations are likely and could be unforeseen.

“We understand the frustration and disruption Balpa’s strike action has caused our customers,” said BA in a statement. “After many months of trying to resolve the pay dispute, we are extremely sorry it has come to this. We remain ready and willing to return to talks with Balpa.

“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% of our flights.”

Balpa said its offer to hold talks last Wednesday (4 September) was ignored by BA, and further offers to hold meetings at Acas on Friday (6 September) “were refused”.

General secretary Brian Strutton said: “British Airways needs to wake up and realise its pilots are determined to be heard. They’ve previously taken big pay cuts to help the company through hard times. Now BA is making billions of pounds of profit, its pilots have made a fair, reasonable and affordable claim for pay and benefits.

“Balpa has consistently offered up chances for the company to negotiate a way forward. British Airways must now put the needs of its staff and passengers first and accept that its pilots will not be bullied or fobbed off.

“This strike will have cost the company considerably more than the investment needed to settle this dispute. It is time to get back to the negotiating table and put together a serious offer that will end this dispute.”