Travellers wait stranded at Heathrow Airport Terminal 5 after British Airways flights were cancelled at airport in west London on May 27. (AFP)

British Airways (BA) said “many” of its IT systems were back up and running Sunday, but travelers still faced cancellations and delays after a global computer failure grounded hundreds of flights. BA chief executive Alex Cruz said the airline was running a “near-full operation” at London’s Gatwick Airport and planned to operate all scheduled longhaul services from Heathrow.But he said there will still be delays, as well as some canceled short-haul flights. BA canceled all flights from Heathrow and Gatwick Saturday after the IT outage, which it blamed on a power-supply problem. The glitch threw the plans of thousands of travelers into disarray, on what is a holiday weekend in Britain. BA operates hundreds of flights from Heathrow and Gatwick on a typical day — and both are major hubs for worldwide travel.Cruz apologized in a video statement, saying “I know this has been a horrible time for customers.” Passengers faced hours-long lines to check in, reclaim lost luggage or rebook flights at Terminal 5, BA’s hub at Heathrow. Cruz said that to reduce overcrowding travelers will only be let into the terminal 90 minutes before their flights.Passengers — some of whom had spent the night at the airport — faced frustrating waits to learn if and when they could fly out. While not that frequent, when airline outages do happen, the effects are widespread, high-profile and can hit travelers across the globe. BA passengers were hit with severe delays in July and September 2016 because of problems with the airline’s online check-in systems. (AP)