A technical meltdown in UK air traffic control has left thousands of passengers stranded or delayed at airports on the summer bank holiday.
About 500 flights were cancelled by early Monday afternoon, with others delayed for hours as takeoffs and inbound flights were suspended due to a “network-wide” computer failure.
Nats, the national airspace controllers, announced at 3.15pm that it had “identified and remedied” the fault, which had started affecting flights aabout four hours earlier.
Passengers were told they could face delays of eight to 12 hours while engineers struggled to locate and rectify the problem. A limited number of flights were able to take off but the flow of air traffic was severely restricted, with controllers forced to input flight plans manually.
According to flight tracking sites, planes were largely delayed at London Heathrow, the UK’s busiest airport, from about 11.30am.
Nats confirmed the problem at about 12.10pm, saying it was “currently experiencing a technical issue” and had “applied traffic flow restrictions to maintain safety”.
In an updated statement it said: “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.
“The flight planning issue affected the system’s ability to automatically process flight plans, meaning that flight plans had to be processed manually which cannot be done at the same volume, hence the requirement for traffic flow restrictions.
“Our priority is always to ensure that every flight in the UK remains safe and we are sincerely sorry for the disruption this is causing. Please contact your airline for information on how this may affect your flight.”
According to data from analytics firm Cirium, 232 outbound flights from the UK and 271 inbound flights had been cancelled by 2.30pm, just under 10% of all services, but the figure was expected to grow as the problem persisted.
A Heathrow spokesperson said: “As a result of national airspace issues there is disruption to flights across the UK. We are working closely with Nats and other airport partners to minimise the impact this has on passengers.”
British Airways told passengers that its flights were subject to delays. A spokesperson added: “We are working closely with Nats to understand the impact of a technical issue that is affecting UK airspace, and will keep our customers up to date with the latest information.”
Holiday giant TUI warned its customers to expect “significant delays to some of our flights” from the airspace issue over the last bank holiday weekend of summer.
The Glasgow-based regional carrier Loganair warned customers on X, formerly known as Twitter: “There has been a network-wide failure of UK air traffic control computer systems this morning.” It said regional Scottish flights could operate but international flights could be delayed.
Flights from Ireland were also affected and delayed with many due to cross UK airspace.
As well as holidaymakers, passengers affected by delays included many people returning from the World Athletics Championships in Hungary.
The BBC presenter Gabby Logan said on X that her plane was stuck on the runway at Budapest airport, adding: “After almost three weeks away from home I am hours from hugging my family. And have just been told UK airspace is shut. We could be here for 12 hours. So we sit on the plane and wait.”
Engineers at Nats will be racing against the clock, with an extended outage likely to spell widespread cancellations. A computer glitch at the control centre in Swanwick in 2014 affected flights until the following day, despite airspace being curtailed only for about an hour.
Labour and the Liberal Democrats questioned the government’s apparent slow response. The transport secretary, Mark Harper, later posted on X that ministers were “doing all we can”.
Harper said: “UK airspace remains open but traffic flow restrictions are in place. Nats are working at pace to fix this and aviation minister [Charlotte Vere] and I are doing all we can to support them.”
Earlier, Labour’s shadow transport secretary, Louise Haigh, posted that the issue was “extremely concerning for passengers travelling in and out of the UK on one of the busiest days of the year”, adding that she was “surprised” by the lack of a ministerial statement.
The Lib Dems called on the prime minister to convene a Cobra meeting. The party’s transport spokesperson, Wera Hobhouse, said: “Millions of holidaymakers could be facing huge disruption in the coming days due to this fault and we can’t risk this government being missing in action yet again.”