British Airways has warned it would take some time for its flight schedule to return to normal after a pilots strike this week left aircraft and crew in the wrong place.
This could mean further disruption for passengers.
Owned by International Airlines Group (IAG), British Airways was forced to cancel 1,700 flights to and from London's Heathrow and Gatwick airports during two days of action this week, in its latest high-profile setback. IAG also owns Aer Lingus.
The action was brought by British Airline Pilots Association (BALPA) members in a dispute over pay. The union wants a pay deal to include profit sharing for BA pilots.
"We are working hard to get back to normal and to get our customers to their destinations," the airline said in a statement.
"The nature of our highly complex, global operation means that it will take some time to get back to a completely normal flight schedule however, we plan to fly more than 90% of our flights today," it added.
As a result of the strike, nearly half of BA's fleet of over 300 aircraft and more than 700 pilots will start the day in the wrong place.
In addition, more than 4,000 cabin crew faced disruption to rosters, meaning some will need to take time off for legal rest requirements.
BALPA has estimated that the strike action cost the airline around £40m a day.
It has sparked a backlash on social media from customers who criticised the airline's handling of events, and caps a tough few years after several operational failings.
In August BA suffered its third major computer failure in little more than two years, disrupting flights during the peak travel period.
It also faces a record $230m fine under tough new data-protection rules after the theft of data from 500,000 customers from its website last year.
Following strikes on Monday and Tuesday, another day of industrial action is scheduled for September 27.