British Airways have started to cancel flights ahead of the next pilots strike on 27 September.
The strike action will affect hundreds of flights and thousands of passengers, BA has started to contact customers affected.
A BA spokeswoman said the decision was made “to give customers as much certainty as possible.”
“We are very sorry that Balpa’s actions will affect thousands more travel plans. “We urge them to call off their strike and return to negotiations.”
Earlier this week pilots walked out for two days costing BA £40m per day and causing almost 200,000 passengers to change their travel plans.