Thousands of travellers have been stranded after British Airways' online check-in system crashed due to an IT glitch.
The airline apologised to customers for the disruption and said its technical team was working to resolve the problem.
"We are experiencing some systems problems this morning which are affecting check-in and flight departures," it said.
"This is affecting other systems as well."
Just over a year ago, BA was forced to cancel flights at Heathrow, due to problems with a supplier's IT system.

Lebanon, Israel conclude US-brokered talks in Rome
US launches new round of strikes against Iran
Zelenskyy endorses energy boss as new Ukraine prime minister
Trump resumes Iran port blockade, threatens strikes on energy targets
