NATS provides air traffic control services and solutions to some of the UK’s largest airports, and also manages UK upper airspace.

In a statement from Martin Rolfe, the chief executive of NATS, it was revealed that initial investigations had shown that there was an issue with flight plan data which was received.

NATS’ primary and backup systems responded to the issue by suspending the automatic processing of flight data, so that incorrect safety-related information couldn’t be presented to an air traffic controller, or impact the rest of the air traffic system.

However, due to Monday’s technical issue, air traffic flow restrictions were applied, thereby leading to flight delay and cancellations across the UK network — including inbound and outbound flights.

In his statement, Role wanted to reassure the public that “all of our systems have been running normally to support airline and airport operations as they recover from this incident.”

He also stated that NATS has “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.”

Rolfe specifically noted that “There are no indications that this was a cyber-attack.”

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While there’s never a good time for such a technological fault, the timing of Monday’s issue was particularly inopportune, considering the Summer Bank Holiday across England, Wales, and Northern Ireland, and the winding down of the Edinburgh Fringe festival in Scotland.

“While we resolved the problem quickly, I am very conscious that the knock-on effects at such a busy time of year are still being felt by many people travelling in and out of the UK,” Rolfe noted.

Ryanair’s CEO, Michael O’Leary, said that the airline had to cancel “about 250 flights” on Monday, affecting about “40,000 passengers” because of “long delays to flight plans,” and “crews running out of hours.”

On Tuesday, the following day, O’Leary said that it would look like Ryanair would “cancel about another 70 flights.”

According to the BBC, and concerning the UK’s six busiest airports, analysis of flight data websites has shown that at least 281 flights were cancelled on Tuesday.

This included 75 at Gatwick, 74 at Heathrow, 63 at Manchester, 28 at Stansted, 23 at Luton, and 18 at Edinburgh.