Martin Rolfe, NATS CEO, said: “I would like to apologise again for our technical failure yesterday. 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.
"I would like to reassure everyone that since yesterday afternoon all of our systems have been running normally to support airline and airport operations as they recover from this incident.
"NATS exists to allow everyone flying in UK airspace to do so safely. Our systems enable our air traffic controllers to deliver this service all year round. These have several levels of backup and allow us to manage around 2 million flights per year in some of the busiest and most complex airspace in the world safely and efficiently.
"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. I would like again to apologise to everyone who has been affected.”