British Airways pilots have announced they will go on strike on three dates in September.
The British Airline Pilots Association (Balpa) has given notice to the airline that it will call on its members to walkout September 9, 10 and 27.
BA has said the action is “completely unacceptable” and warned many customers would not be able to travel.
Balpa said it put forward a number of packages that it believed would have resolved the dispute but BA did not accept them.
“It is clear following discussions with members over the last few days that BA’s most recent offer will not gain the support of anywhere near a majority of its pilots,” the union said.
“In these circumstances, with a 93% vote in favour of taking industrial action, and with no prospect of any further meaningful talks, we have no choice but to call this action.”
Balpa said it would cost BA around £120m.
In a statement, BA said: “It is completely unacceptable that Balpa is destroying the travel plans of tens of thousands of our customers with this unjustifiable strike action.
“Balpa has given us notice that they will strike on September 9th, 10th and 27th. We are extremely sorry that after many months of negotiations, based on a very fair offer, BALPA has decided on this reckless course of action.
“We are now making changes to our schedule. We will do everything we can to get as many people away on their journeys as possible. However, it is likely that many of our customers will not be able to travel and we will be offering refunds and re-bookings for passengers booked on cancelled flights.”
The airline said flights on BA CityFlyer, SUN-AIR and Comair would not be affected.
It said it is exploring options to supplement its fleet by using aircraft and crew from other airlines and working with partner airlines to schedule larger aircraft to take the maximum number of customers.
“Our proposed deal of 11.5 per cent over three years is very fair and well above the UK’s current rate of inflation, and by contrast to Balpa, has been accepted by the members of the Unite and GMB trade unions, which represent nearly 90% of all British Airways colleagues including engineers, cabin crew and ground staff. In addition to basic pay, pilots also receive annual pay increments and regular flying allowances.
“We continue to pursue every avenue to find a solution to avoid industrial action and protect our customers’ travel plans.”