A global computer outage struck British Airways' systems early Saturday, at the beginning of a busy holiday weekend in both the U.S. and the United Kingdom, forcing the airline to cancel all flights leaving both London Gatwick and London Heathrow airports.
BA said that those unable to fly would be offered a full refund, warning that some delays and disruption could continue into Sunday.
One traveller, PR executive Melissa Davis, said she was held for more than an hour and a half on the tarmac at Heathrow aboard a BA flight arriving from Belfast.
British Airways GMB union has blamed the airline's 2016 decision of outsourcing IT jobs to India as the reason behind cancelling all Saturday flights from London's two biggest airports: Heathrow and Gatwick.
Passengers also reported long queues at check-in gates at Heathrow Airport.
The airline said it was "extremely sorry" for passengers' inconvenience and was working to resolve the problem as soon as possible. Passengers at British airports yesterday said they had boarded flights but then were stuck on the runway. It advised passengers booked on flights scheduled to leave Sunday morning to check the status of their flight ahead of their scheduled departure time.More news: EPA's Pruitt says leaving Paris Accord is about jobs, not politics
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All of BA's check-in and operational systems have been affected by the issue, including the airline's customer service phone lines and rebooking function.
Thousands of passengers were stranded on Saturday at Heathrow and Gatwick after planes were grounded by a major systems failure believed to have been caused by a power supply issue.
The outage comes amid a busy weekend for travel, with Monday being a holiday in both the United Kingdom and the United States.
Major problems with BA's systems led to disruption for thousands of passengers as all flights from Heathrow and Gatwick were cancelled yesterday.
The airline said it was working to restore services out of Heathrow and Gatwick beginning Sunday, although there will still be some disruptions.
The GMB union said the airline's decision to outsource hundreds of IT jobs to India a year ago was behind the problems, the Guardian reported.