British Airways has advised passengers flights are likely to be cancelled as pilots prepare to strike on Monday and Tuesday.
Pilots forming part of union Balpa (British Airline Pilots Association) voted in favour of walking out after failing to reach an agreement with the airline, which offered an 11.5% pay rise over three years.
Strike action is planned on Monday and Tuesday, and also for September 27, after the airline lost a Court of Appeal bid to stop the pilots walking out.
Last month, when the strike dates were announced, the airline said it was "likely" anybody booked on those days will not be able to travel.
BA said it is “extremely sorry” and told customers affected they can expect a full refund.
Passengers should find out via email whether their flight is definitely cancelled.
Options on what to do next can also be found by logging into the BA website and visiting the Manage My Booking page.
Customers with flights on Monday and Tuesday can rebook cancelled trips or claim a refund on the British Airways website.
BA pilots are also set to strike on September 27.
Anyone flying on this day will be told in the next few weeks if their flight is impacted.
“Our customer teams – supported by additional colleagues - have been working tirelessly to help as many of you as possible and to provide options, including a full refund or re-booking to a different date of travel or alternative airline,” a statement said.
“We continue to be available for constructive talks with Balpa, on the basis that there are no pre-conditions to those talks.
“If you have a flight booked with us on those dates, it is likely that you will not be able to travel as planned due to Balpa’s strike action.
“We are offering all affected customers full refunds or the option to re-book to another date of travel or alternative airline.”
The union said pilots should be given a greater share of the “massive profits”, in part for their sacrifices and efforts to help the airline recover from recent struggles.
BA defended the offer as “fair” and said it had already been endorsed by the Unite and GMB trade unions to the almost 90% of BA staff they represent.