An air traffic control failure that led to major disruptions for passengers on Monday and Tuesday was caused by flight data received by National Air Traffic Services (Nats), the body has said.

Thousands of passengers were left facing severe delays to their journeys, with some forced to sleep overnight at airports throughout Europe before finally reaching home.

Martin Rolfe, Nats chief executive, said: “The air traffic control failure was caused by flight data received by National Air Traffic Services, with both primary and back-up systems responding by suspending automatic processing.

“Very occasionally technical issues occur that are complex and take longer to resolve. In the event of such an issue our systems are designed to isolate the problem and prioritise continued safe air traffic control.

“This is what happened yesterday. At no point was UK airspace closed but the number of flights was significantly reduced. Initial investigations into the problem show it relates to some of the flight data we received.

“Our systems, both primary and the back-ups, responded by suspending automatic processing to ensure that no incorrect safety-related information could be presented to an air traffic controller or impact the rest of the air traffic system. There are no indications that this was a cyber-attack.

“We have well-established procedures, overseen by the CAA, to investigate incidents. We are already working closely with them to provide a preliminary report to the Secretary of State for Transport on Monday. The conclusions of this report will be made public.”

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