Pilots at British Airways will go on strike for three days in September after talks failed to settle a long-running pay dispute, the union has announced.

The pilots will take industrial action on 9, 10 and 27 September in a move that BA said was likely to disrupt the plans of “tens of thousands” of passengers.

The British Airline Pilots’ Association (Balpa) said the airline had rejected its proposals to resolve the standoff and it had “no choice but to call this action”. The airline said it had offered a three-year deal of 11.5% that had been accepted by other BA employees, and it would “continue to pursue every avenue to find a solution to avoid industrial action”.

The union said 93% had voted in favour of industrial action and there was no prospect of further meaningful talks. It urged the airline to seek an agreement but warned that further strikes were possible.

The strikes are likely to cost the airline about £40m a day; they take place in what is British Airways’ centenary year.

Balpa said pilots had made previous sacrifices to assist the company including cuts to salary, pension and leave, but the airline was now recording profits of £2bn a year and the strike was “a last resort and with enormous frustration at the way the business is now being run”.

BA’s chief executive, Alex Cruz, said he was “sad and disappointed” by what he called a totally unnecessary strike.

He said: “The blame lies squarely at the door of the pilots’ union, Balpa. I personally believe BA pilots are the best in the world … But I think they have been very badly served by the union.”

A BA captain earns an average of £167,000 and, with allowances and bonuses, would pass £200,000 per year after the three-year pay deal, Cruz said.

He added that the airline would be contacting affected passengers within the next 36 hours, but passengers could make their own re-bookings now online, and that cancellations were bound to occur.

BA plans to hire planes and crew from other airlines, and schedule larger aircraft on codeshare flights – where two or more airlines share the same flight – to allow as many passengers as possible to travel.

BA sought an injunction to stop the strike, but its claim was rejected in the high court and again at appeal last month.

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