British Airways has gone to the High Court in a bid to block pilots from taking strike action it says will be “enormously disruptive” during the summer holiday period.

The British Airline Pilots’ Association (Balpa) announced on Monday that its members backed industrial action over a pay dispute by more than nine to one, on a turnout of 90%.

BA has now taken legal action in an attempt to halt the strikes, which it claims are designed to cause “the maximum in disruption” and could cost the airline up to £40 million a day.

On Tuesday, BA applied for an interim injunction to prevent strike action by pilots based at Heathrow and Gatwick, arguing that Balpa’s ballots did not comply with trade union law.

The airline’s barrister John Cavanagh QC said Balpa did not provide a list of the categories of employees who had been balloted, arguing that the union’s failure to specify whether pilots were in long-haul or short-haul fleets meant it could not rely on the ballot.

He also argued that Balpa did not indicate when the strike action would take place, which he said was “likely to commence on or about August 7”.

Mr Cavanagh said: “There can be no doubt that the timing of the action is deliberate and designed to cause the maximum in financial loss and disruption for BA, and the maximum in disruption and hardship for BA’s passengers (and those they are going to visit), plus business partners and other employees.

“The action is due to commence in peak holiday period, in the middle of school summer holidays, and at the busiest time of BA’s year.”

He told the court that BA would take steps “to mitigate the consequences of the strike action”, but said: “There is no doubt that if the industrial action takes place there will be very grave disruption indeed.”

Mr Cavanagh added: “It is impossible accurately to assess BA’s financial loss if the industrial action were to go ahead, save that it will be very substantial indeed, running to £30-40 million per day.”

In written submissions, Balpa’s barrister Simon Cheetham QC argued that trade unions have “a degree of discretion as to how it categorises workers”, and that Balpa “was only required to set out general job categories”.

He added that the categories Balpa provided “closely (matched) the titles and positions given by BA in its corporate directory”.

Mr Cheetham said the level of detail BA argued Balpa was required to provide amounted to “a disproportionate interference with the right to strike”.

He also submitted that the union was not required to provide the dates of its strike action, saying: “The only duty is to provide the period or periods within which the industrial action is expected to take place.”

Mr Cheetham said Balpa had not yet decided when strike action would take place, and that the union “wishes to have the power to call industrial action at any time during the period between August 7 and January 21 (2020), the maximum period during which the ballot is valid”.

The hearing is expected to last most of Tuesday, and it is unclear whether Mrs Justice Elisabeth Laing will give a ruling today or on Wednesday.

In a statement after the ballot result was announced on Monday, Balpa general secretary Brian Strutton called on BA to “table a sensible improved offer if a strike is to be averted”.

BA said its offer to pilots was worth 11.5% over three years, adding: “We are very disappointed that Balpa has chosen to threaten the travel plans of thousands of our customers, over the summer holidays, with possible strike action.

“We remain open to working with Balpa to reach an agreement, which we have been doing since December.”