Flights from British airports resumed early Wednesday following a major air traffic control failure, but operators warned a full return to normal operations would take time as scrutiny of the reliability of Britain's aviation systems intensified.
The hours-long outage Tuesday, which resulted in the cancelation of more than 1,000 flights and left hundreds of thousands of passengers stranded, has ramped up pressure on air traffic control provider NATS and its boss Martin Rolfe.
Transport Minister Heidi Alexander will later Wednesday hear from Rolfe after she summoned him to explain what happened, amid concerns that the infrastructure and technology are not up to scratch.
The shutdown comes three years after the last system meltdown in August 2023, when canceled flights on one of the busiest travel days of the year cost airlines 100 million pounds ($135 million).
A radar-related technical issue also disrupted flights in July 2025, affecting major airports including Britain's largest, Heathrow.
"I am seeking assurances that lessons will be learned and systems that support aviation are up to the job," Alexander said on the social media platform X.
Ryanair, Europe's biggest airline, has been calling for Rolfe to resign since 2023, while Wizz Air's U.K. managing director also said he should consider his position.
Ryanair said Britain's airspace underperformed other countries.
"We've had minor issues in other places, but nothing at the scale that we see, and consistently see, in the U.K.," Ryanair's chief operating officer Neal McMahon told the BBC.
Rolfe, who apologised to those affected by the issue, denied that Britain was worse than other countries and said the country's air traffic service was well regarded from a safety and resilience perspective.
"We have, at this point, ruled out cyber(attacks)," Rolfe told the BBC when asked about the cause, adding he believed it would be different to previous outages.
As operations restarted, Heathrow said passengers should check with their airline before heading to the airport as schedules would have changed due to the problems on Tuesday.
"We are expecting knock-on impacts as aircraft and crew reposition," the U.K.'s busiest hub said in a statement.
"We... are 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, and the city's Luton and Stansted also said they were operating but told passengers to check with their airline first.
Ryanair said around 150,000 of its passengers had been affected Tuesday and it canceled more than 200 flights, while British Airways said it had canceled or diverted 100 flights with tens of thousands impacted.
NATS is a public-private partnership which is partially owned by airlines including British Airways and easyJet, pension funds and the government.
Criticizing the 175 million pounds of dividends NATS paid to its owners last year, Ryanair's McMahon said NATS should reinvest its profits into technology and boost its staff numbers.
