British Airways owner IAG says the strikes called by pilots in a dispute over pay and conditions have cost it at least €137m (£120m).
As a result of the two-day strike by pilots on 9 and 10 September, IAG said a total of 2,325 flights had been cancelled.
There have been no further talks between BA and the union, and more strikes will hit profit, IAG said.
In addition, IAG took a €33m hit over threatened strikes at Heathrow Airport.
Overall, IAG expects its operating profit for this year to be €215m lower than in 2018.
This includes a €45m hit from lower bookings and yields – a measure of the average fare per passenger mile – on IAG’s low cost Vueling and Level airlines.
Shares in IAG were among the biggest losers on the FTSE 100 in early trading, dropping about 3.7%, before paring some losses.
A strike by BA pilots that had been scheduled for 27 September was called off last week. At the time, the British Airline Pilots Association (Balpa) said it was now time for a period of reflection before the dispute “escalates further and irreparable damage is done to the brand”.
Balpa has said strike action is a “last resort” due to “enormous frustration” with the management of the airline.
Pilots rejected a pay increase worth 11.5% over three years, which BA proposed in July.
Balpa says its members took lower pay rises and made other sacrifices during tougher times for the airline, and now that BA’s financial performance has improved – IAG reported a 9% rise in profits last year – they want a greater share of the profits.
Thomas Cook slots
In a call with analysts, IAG chief executive Willie Walsh said the airline group was interested in slots at Gatwick that may be up for grabs following the collapse of travel firm Thomas Cook.
“If there’s an opportunity to acquire some slots through the administration process, we will be looking at that,” he said. “We see Gatwick as an opportunity for us.”
The 178-year-old holiday firm collapsed on Monday after rescue negotiations failed, triggering the biggest peacetime repatriation to bring 150,000 UK holidaymakers home.