The head of the air traffic control provider Nats has been given a week to report back on the reasons for the technical failure that has disrupted thousands of flights since Tuesday.Downing Street said the government still had confidence in Nats chief executive Martin Rolfe, who was summoned to meet the UK transport secretary, Heidi Alexander, on Wednesday morning as the number of flight cancellations passed 2,000.Rolfe has been facing increasing pressure to quit after the third large-scale stoppage to flights in just over three years.Hundreds of thousands of passengers had their travel disrupted and delayed, with many stuck on grounded planes for many hours as the incident unravelled. Other passengers were stranded overnight at airports in the UK and abroad.Alexander raised “significant concerns” with Rolfe, according to the prime minister’s official spokesperson, who told reporters: “She’s asked him to carry out a full investigation into what happened to make sure that lessons are learned, so that this doesn’t happen again.”They added: “It’s self-evident that she wants answers and the full investigation to be reported back in a week’s time, and she’s got confidence in him to deliver that.”Pressed on whether the government’s confidence in the head of air traffic control was conditional on the investigation, the spokesperson replied: “We have confidence in him and he’s been tasked with the investigation, which will report in a week’s time.”Airlines including Ryanair and Wizz have called for Rolfe to resign or be sacked by Alexander.Rolfe earlier ruled out a cyber-attack as a cause for the “technical issue” at air traffic control and defended the resiliency of the systems run by Nats, which provides services to 15 UK airports.“We will be doing a very thorough and full investigation,” he told BBC Radio 4’s Today programme. “We have at this point ruled out a cyber-attack.”Nats said the problem occurred in its flight processing system but was not the same fault as those that caused outages and mass disruption in 2023 and 2025.However, Ryanair queried the explanation and said lessons had not been learned. The carrier, which on Tuesday said more than 65,000 of its passengers had been disrupted when 50 flights were cancelled, said it had now cancelled more than 250 flights and its costs would run into millions.The airline’s chief executive, Michael O’Leary, said: “Martin Rolfe’s position as Nats CEO is untenable. We don’t need more investigations, we don’t need more reports, and we don’t need another parliamentary committee hearing where Martin Rolfe will promise change, will promise resilience, and will promise an effective backup system.”He said that the UK’s air traffic control services were one of the most expensive in Europe “and yet it keeps repeatedly failing”. O’Leary said Alexander should “today demand that failing Martin Rolfe must quit, or be dismissed”.Yvonne Moynihan, the managing director of Wizz Air UK, called on Rolfe to consider resigning.“In any industry when you’ve had three failures, you need to consider three strikes and you’re out,” she told Today.“A third time and a third excuse is not enough any more. What we need to see from leadership is accountability. ”Luke Petherbridge, director of public affairs at the travel association Abta, said: “While the immediate priority is supporting customers … the industry and the public will want answers as to what has gone wrong, what lessons are being learned, and how the system will be made more resilient to avoid this happening again.”skip past newsletter promotionafter newsletter promotionNats said that the fix it eventually implemented on Tuesday, almost four hours after the incident first occurred, had been a “very complex recovery and has created difficulties for the whole aviation network, from which it will take time to recover”.More than 300 flights were cancelled by Wednesday lunchtime in the continuing fallout from the outage.According to data from the analysts Cirium, more than 2,000 flights in and out of UK airports have been cancelled because of the failure, including 1,750 on Tuesday out of 5,800 scheduled flights. Of these, 541 were at Heathrow.In a statement on social media on Wednesday morning, Heathrow said: “Following yesterday’s Nats technical issue, flights are operating today, but some disruption may continue as airlines reposition aircraft and crew.“Please check your flight status with your airline before travelling to the airport and only travel if your flight is confirmed to be operating.”Gatwick also said flights had resumed but the disruption was likely to continue.Rail passengers affected by flight disruption can use booked tickets on a different date or to a different airport if needed, or apply for a refund, the Rail Delivery Group said.The breakdown started at about 1pm on Tuesday and affected departing flights at many of Britain’s biggest airports, including Heathrow, Gatwick, Manchester and Stansted.London airports, as well as Manchester, were among the most directly affected, with operations effectively suspended for hours in the afternoon. While Heathrow said the fault initially only stopped takeoffs, the airport was soon too full to accommodate more planes, with arriving flights diverted around European airports.Flights to and from other airports around the UK, including Birmingham, Edinburgh and Belfast, were also disrupted.The air traffic control problems follow an “isolated event” a year ago that caused widespread disruption, and appeared less severe than the full grounding of flights in August 2023, which prompted a parliamentary inquiry.