British Airways is working to restore its computer systems after a power failure caused major interruption for thousands of passengers worldwide.
The airline is “closer to full operational capacity” after an IT power cut resulted in mass flight cancellations at Heathrow and Gatwick.
Thousands of passengers remain displaced, with large numbers sleeping overnight in terminals.
BA has not explained the cause of the power problem.
So far on Monday, 13 short-haul flights at Heathrow have been cancelled.
Heathrow advised affected BA passengers not to travel to the airport unless their flights had been rebooked, or were scheduled to taken away from today.
Passengers on cancelled flights have been told to use the BA website to rebook.
Chief executive Alex Cruz has posted videos on Twitter apologising for what he called a “horrible time for passengers”.
But no-one from the airline has been made available to answer questions about the system crash, and it has not explained why there was no back-up system in place.