More than 400 flights were canceled on Tuesday due to a technical issue in Britain's air traffic control system, the flight monitoring website Flightradar24 reported.
Britain’s National Air Traffic Services said a problem had been identified in its flight processing system and engineers were urgently working on the issue, which affected flights across the U.K.
In an update, it said it had “implemented a fix and our flight system is starting to recover.”
About 425 flights to and from U.K. airports, including Heathrow, were canceled, affecting services operated by multiple airlines, including British Airways, EasyJet, KLM and Lufthansa.
The affected airports, which also included Stansted and City in London, as well as airports in Manchester, Birmingham and Scotland, said the technical issue caused disruptions. They warned passengers to check the status of their flight with their airline.
Budget airline EasyJet said some of its flights were “unable to operate” and that the system failure caused “delays to flights across Europe.”
Some passengers took to social media to complain about being stuck on the tarmac for hours. Many expressed frustration about a lack of communication from airlines.
Heathrow's website showed that many short-haul flights departing for European destinations had been canceled or delayed.
Arriving flights did not appear to be affected. It was not immediately clear what caused the technical problem.
