A technical fault at UK air traffic control service provider Nats disrupted hundreds of flights across major British airports on Tuesday, with around 300 cancellations reported and delays continuing into the evening.

Departures from London airports were most severely affected, with few take-offs recorded after the fault was reported early on Tuesday afternoon. Airports hit by the disruption included Heathrow, Gatwick, Manchester, Stansted, London City, Edinburgh, Birmingham, Bristol and Belfast.

Flight monitoring service Flightradar24 reported approximately 300 flights cancelled. Analytics company Cirium said around 90 flights in and out of Heathrow and Gatwick alone had been cancelled by 4.15pm.

Nats said at 1.46pm it was "investigating a technical issue which is causing some disruption to flight departures." The agency later identified the problem within its flight processing system and announced at 4.40pm that a fix had been implemented.

However, Nats cautioned that the system was only "starting to recover," adding: "We are continuing to work closely with our airline and airport customers on recovery. We apologise sincerely for the disruption to people's journeys today and they should continue to check with their airline."

Heathrow initially said only departures were affected, but later confirmed the Nats issue was "impacting arriving and departing flights across UK airports." The airport advised passengers to check with their airline and "only travel to the airport if their flight is confirmed."

Ryanair said more than 65,000 passengers had been delayed and 50 flights cancelled. The knock-on effects spread across Europe, with European air traffic organisation Eurocontrol reporting that some inbound flights were being held at airports abroad, with disruption likely to continue into the evening.

British Airways said it was experiencing some disruption and was in contact with affected customers. Birmingham airport advised passengers to arrive in line with their airline's check-in requirements and to contact their airline directly for updates. Edinburgh airport said it was aware of the issue and that it "may impact operations."

Transport Secretary Heidi Alexander said: "I'm aware of a technical issue impacting flights at airports including Heathrow and Gatwick. Technicians have identified the issue and are fixing it as we speak. I know this will be frustrating for passengers and I'm sorry."

The incident is the third major Nats disruption in just over three years. It follows an isolated event a year ago and appears less severe than a full grounding of flights in August 2023, which prompted a parliamentary inquiry.

Airlines renewed calls for Nats to be overhauled in the wake of the latest failure. Ryanair repeated its demand for Nats chief executive Martin Rolfe to resign. The airline's chief operating officer, Neal McMahon, said: "Families travelling on holiday, people travelling for work and thousands of visitors to the UK have once again paid the price for Nats' abhorrent failure."

McMahon called on the government to "stop making excuses for repeated Nats failures and appoint a new leader capable of running the UK ATC system."

Wizz Air also issued a sharp rebuke, stating: "A critical national infrastructure provider should not repeatedly bring the aviation system to a standstill. Nats is simply not fit for purpose in its current form."