Analysts said the disruption — on a national holiday in Britain and during a peak end-of-summer travel period — affected hundreds of flights on Monday alone. About 1 million people had been booked to fly in and out of the U.K.
Britain’s National Air Traffic Service (NATS) reported that the IT issue had shut down automated flight planning throughout the country, including at London’s Heathrow, one of the busiest international airports in the world.
NATS said it never closed down U.K. airspace but applied “traffic flow restrictions” while air traffic controllers had to revert to manual systems to sequence plane departures and landings.
“We are now working closely with airlines and airports to manage the flights affected as efficiently as possible. Our engineers will be carefully monitoring the system’s performance as we return to normal operations,” NATS said Monday afternoon.
The European air control agency, Eurocontrol, warned of “very high” delays because Britain was experiencing “a flight data processing system failure.” Ireland’s air traffic controller, AirNav Ireland, said in a statement that there were “significant delays for flights across Europe that are traveling to, from or through UK airspace.”
Cirium, an aviation analytics firm, said in an email that data on cancellations at U.K. airports was coming in “thick and fast” and that it would release more comprehensive figures on Tuesday.
Even then, cancellations and delays are expected to continue, as some planes and flight crews won’t be in place to fly their scheduled routes.
British officials said it was not immediately clear what caused Monday’s system failure.
After a software issue caused a nationwide grounding of planes in the United States in January, the Federal Aviation Administration said contractors had mistakenly deleted files, impacting the system that sends messages to pilots.
Aviation experts in Britain said Monday’s system failure was both unusually disruptive and predictable.
“Any glitch that impacts approximately 1 million passengers is a serious issue,” said Paul Charles, an aviation expert. “These systems should not be falling over, especially on one of the busiest days of the year.”
“It’s a symbol of our wider IT infrastructure, creaking at the seams,” he said, suggesting that there had been a lack of investment during the coronavirus pandemic, when travel slowed.
Last year, 37 percent of flights in and out of the U.K. were at least 15 minutes late — delays that Britain’s Civil Aviation Authority called “unacceptable.”
In May, a technical fault with Britain’s automated border control gates, or e-Gates, caused major delays at airports.
Passengers caught up in the chaos on Monday shared their experiences.
The Washington Post’s Jennifer Hassan boarded an EasyJet plane in Inverness, Scotland, on Monday morning, destined for London Luton Airport. But after nearly two hours on the tarmac, passengers were asked to disembark and were warned to expect a six- or seven-hour delay.
By evening, those passengers were encouraged to find their own hotels.