The chaos that hit British airports on Friday was sparked by an unprecedented systems failure, it was disclosed yesterday.
Air traffic control company Nats has given its first detailed explanation of the problem at its national centre in Swanwick, Hampshire, that saw dozens of flights cancelled and delayed.
It said: “Swanwick controller workstations provide a number of tools and services to the controller to enable them to safely control a high volume of air traffic.
“In normal operations the number of workstations in use versus in standby fluctuates with the demands of the traffic being controlled.
“In this instance a transition between the two states caused a failure in the system which has not been seen before. The failure meant that the controllers were unable to access all of the data regarding individual flight plans which significantly increases their workload.
“Our priority is to maintain a safe operation for the flying public; consequently when the failure occurred we immediately took steps to reduce the traffic into and out of the UK network.
“The controllers had a full radar picture and full communications with all aircraft at all times during the incident and at no time was safety compromised in any way.”
Gatwick reported that there had been 16 cancellations and seven diversions of inbound flights
Nats said it understood the problem was connected to a number of workstations “in a certain state” combined with the number of “air space sectors” open.
Officials restricted air space in response to the issue, leaving flights at some airports grounded on Friday.
Nats declared that its systems were back to full operational capacity on Friday night but a knock-on effect was seen at airports yesterday.
Heathrow said 38 flights had been cancelled before 9.30am.
In a statement, the airport said: “Following yesterday’s technical problem at the Nats air traffic control centre in Swanwick, operations have started up well at Heathrow on what is a very busy day.
“There will, though, be cancellations to some flights because aircraft and crew are out of position.
“Passengers due to depart today should check the status of their flight with their airline before travelling to Heathrow. We are very sorry for the disruption to passengers’ journeys.”
Gatwick reported that there had been 16 cancellations and seven diversions of inbound flights on Friday but said the airport was running normally yesterday.
A British Airways spokeswoman said: “We’ve been working hard to look after our customers following the air traffic control system failure, yesterday.”