Nats air traffic control system suffered a fault on Tuesday, forcing hundreds of flight cancellations across the UK and affecting tens of thousands of passengers.
Heathrow, Gatwick, Manchester and Birmingham were among the worst-affected airports, with 13 Heathrow-bound flights diverted and airlines cancelling hundreds more.
Nats said the fault was in its flight data processing system, while Transport Secretary Heidi Alexander said a cyberattack was not the cause and warned disruption could continue into Wednesday.
Flight delays are likely to run into Wednesday after an air traffic control fault forced hundreds of cancellations across the UK on Tuesday and affected tens of thousands of passengers. FlightRadar24 reported that as many as 1,000 flights were cancelled after a glitch hit Nats, the UK's air traffic control provider.
Martin Rolfe, Nats' chief executive, apologised and told the BBC there would be a full investigation. Nats stated that resolving the issue had taken "longer than hoped". The BBC understands Transport Secretary Heidi Alexander has called Rolfe to a meeting on Wednesday to answer questions about the disruption and Nats' response.
Alexander is also expected to tell MPs that a cyber attack was "categorically" not the cause. She wrote on X that "it will take time to fully resume flights, so continue to check with airlines" and added: "I am seeking assurances that lessons will be learned and systems that support aviation are up to the job."
What Caused The UK Flight Disruption?
The fallout widened quickly. With few aircraft able to take off, landings were restricted and some flights were unable to depart overseas airports for the UK. Airports in Scotland and Ireland also reported disruption.
EasyJet cancelled 200 flights and British Airways more than 100. FlightRadar24 reported that the worst affected airports were Heathrow, Gatwick, Manchester and Birmingham. Airports across the UK advised passengers to check their flight details before travelling as cancellations and delays continued.
Heathrow was among the worst hit. Departures were paused around lunchtime, then resumed before further disruption in the afternoon. The airport ran out of room for incoming flights because planes had not been leaving, and 13 Heathrow-bound flights were diverted to other airports in the UK and Europe.
According to AP, Nats said the problem had been resolved in the evening, but delays continued to ripple across 15 UK airports and beyond as airlines and airports worked to clear a backlog of delayed flights. Nats resolved the problem in its flight processing system in the evening, although the disruption continued because of the backlog. Heathrow suspended arrivals for the rest of the night because of the disruption and warned of further delays.
Delays rippled across 15 UK airports and beyond. EasyJet said the system failure caused delays to flights across Europe. AP additionally says affected airports included Stansted and London City, along with Manchester, Birmingham, Gatwick and airports in Scotland.
AP explains that the disruption wasn't simply passengers waiting for delayed flights. Aircraft and crews ended up out of position, creating further disruption. British Airways said:. “aircraft and crews ending up out of place.”
British Airways stated that it was expecting knock-on effects. "We were forced to cancel or divert more than 100 flights on Tuesday afternoon," a spokesperson said. "We're doing everything we can to keep our customers updated and make arrangements for them to continue their journeys." "We ask customers whose flights have been cancelled not to travel to the airport and to bear with us if they're trying to get in touch, as our call centres are incredibly busy at the moment."
How Will The Nats Disruption Affect Passengers?
Pressure on Nats increased quickly. Ryanair and Wizz Air called for an overhaul of the organisation, with Wizz Air saying Nats was "not fit for purpose" in its current form. Ryanair, Europe's busiest airline, reported on Tuesday that more than 65,000 passengers had been delayed by up to eight hours.
Rolfe defended the system while promising answers. He said the problem lay in Nats' flight data processing system and that it was not the same system that failed during the August Bank Holiday weekend in 2023. Nats stated that the flight processing system handles flight plans and other operational information used by air traffic controllers and continually updates flight information as aircraft move through UK airspace.
Asked if he was considering his position, Rolfe told the BBC there would be "lots of time for that later". He said his immediate focus was on fixing the problem. Even once the fault is resolved, delays are expected to continue because of backlogs, with arrivals also affected as ground space tightens.
Passengers described long waits. Chloe Davis, 18, from Cambridgeshire, told BBC Your Voice she was stuck on a Virgin plane at Heathrow waiting to fly to Orlando after a scheduled 13:40 (local time) departure. "I'm not concerned, I would just like to know what's going on," Davis said. "There [are] planes parked up on the taxi way because there's no gates for them to go to."
Phil White from Bexhill told BBC Your Voice that his flight to Lanzarote boarded on time but then sat on the tarmac at Gatwick for hours. "We've been told the radar is down and we can't take off," White said. "It's comfortable enough but the pilots been on every 20 minutes saying they are waiting for information from air traffic control and when he finds anything out he will let us know."
