Travel turmoil at UK airports as more than 600 flights are called off.

More than 600 flights were canceled in the U.K. on Tuesday due to a technical issue in the National Air Traffic Services’ flight processing system. The disruption affected major airports such as Heathrow, Stansted, and Manchester, with airlines including British Airways, EasyJet, KLM, and Lufthansa impacted. Passengers reported long waits on the tarmac and limited communication from airlines amidst the cancellations. A fix has been implemented, and the system is beginning to recover, though delays persist across Europe. The root cause of the issue remains unclear.