UK airports began resuming flights early on Wednesday after a major air traffic control failure a day earlier, though operators warned that returning schedules to normal would take time as aircraft and crews needed repositioning.
Tuesday's outage, which stemmed from a technical issue at air navigation provider NATS, forced the cancellation of more than 1,000 flights and left hundreds of thousands of passengers stranded, Reuters reported.
The disruption has intensified pressure on NATS and its chief executive, Martin Rolfe, who was already facing calls to resign from Ryanair over an earlier system failure in August 2023 that cost airlines around £100 million in compensation.
Heathrow Airport, Europe's busiest hub, advised passengers to confirm their flight status with airlines before travelling, as schedules had shifted because of Tuesday's disruption.
"We are expecting knock-on impacts as aircraft and crew reposition," the airport said in a statement, adding that it was "working closely with our local NATS team and airline partners to recover normal operations as quickly as possible."
London Gatwick, Britain's second-busiest airport, issued a similar advisory. Reuters reported that Ryanair said roughly 150,000 of its passengers were affected after it cancelled more than 200 flights, while British Airways said it had cancelled or diverted 100 flights, affecting tens of thousands of travellers.
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The episode marks the latest in a series of technical failures to hit the UK's air traffic control system in recent years. NATS' flight-planning software collapsed in August 2023, delaying or cancelling flights for roughly 700,000 passengers at the height of the summer travel season, while a separate fault at its Swanwick control centre disrupted UK airspace again last year.
Britain's aviation regulator has previously said NATS needs to strengthen its contingency planning after repeated outages.
NATS did not immediately provide additional details on the cause of Tuesday's failure or a timeline for when disrupted schedules across the network would fully normalise.
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