British Airways canceled more than 150 short-haul flights to and from its London Heathrow hub through midday, citing "continuing technical issues" following a systems outage that hit late Friday.
Morning departures to Milan, Geneva and Aberdeen were among those scrapped Saturday, with the carrier predicting further disruption through the day and advising people to check the status of their flight before heading to the airport.
Long-haul services at Heathrow together with flights at London's smaller Gatwick and City airports were due to operate, though with possible delays, BA said in an emailed statement, adding that its website was now working again.
British Airways said Friday that the disruption stemmed from a hardware issue and that it hadn't suffered a cyber-attack. Authorities have been on alert for electronic disruption following Russia's attack on Ukraine. Prime Minister Boris Johnson's government banned Aeroflot flights to Heathrow after the invasion, with Moscow responding by closing its airspace to UK carriers.
BA was criticized on social media, with passengers saying they weren't notified of cancellations and had been unable to reach the carrier's call centers. The airline said those impacted can get a refund or rebook for a later date.
"Our teams have been working hard through the night and will continue to do so to resolve the issue as soon as possible," it said.