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.

Saudi coalition says it intercepts Houthi missiles, drones
WHO says Congo Ebola outbreak spreads to two new health zones
Congo military plane crash kills 13
Kazakhstan detains defence officials after 14 die during naval exercise
Trump, Xi wrap up summit with tea and tour of US archives
