Airlines are attempting to recover their flight operations after an air traffic control (ATC) fault caused major disruption on Wednesday afternoon.
Thousands of passengers have been affected, with many likely to continue facing issues with their journeys.
ATC provider Nats said its systems are “fully operational” and that air traffic capacity is “returning to normal” after the technical glitch affected flights across the UK following restrictions on the number of aircraft which could fly in England and Wales.
ℹ️ Technical issue at Swanwick
— NATS (@NATS) July 30, 2025
Our systems are fully operational and air traffic capacity is returning to normal.
(1/2) https://t.co/69ftwzLeSK pic.twitter.com/KKDercVfqa
Nats is working with airlines and airports to clear the backlog of flights now that departures at all airports have resumed, the company added.
John Carr, a chiropodist from Stourbridge, was on his way to Norway with a group of friends to help set up his brother’s wedding, for which he is best man, when he found out after checking in that his flight was cancelled.
The 35-year-old told the PA news agency at Heathrow Airport: “I’m pretty gutted. We’ve got loads of stuff in the suitcases to set up the venue, because we’re obviously flying to Norway. We’ve got the wedding rehearsal to do. It’s quite stressful.”
He said they did not receive any warning of the cancellation before it happened.
“We had no idea,” Mr Carr told PA.
“There was nothing that the airport had said out on the speaker phones, or anything like that. There was no warning from them or the airline that said it was cancelled. It’s rubbish. There’s nothing we can do.
“We don’t know what we’re going to do tonight in terms of accommodation.
“We have put our cars in special car compounds for the next six days.”
Baptiste, who did not want to give his full name, said he was told his flight had been cancelled while on the tarmac.
He is travelling home to France with his family and told PA: “We have no information. When we arrived, we were stopped on the tarmac and in the plane. We learned that our flight had been cancelled. We’re going to Geneva in Switzerland, so we’re trying to find a flight for tomorrow and a hotel.”
Ryanair called for Nats’ chief executive Martin Rolfe to resign in the wake of the fault, claiming “no lessons have been learnt” since the August 2023 system outage.
The airline’s chief operating officer Neal McMahon said: “It is outrageous that passengers are once again being hit with delays and disruption due to Martin Rolfe’s continued mismanagement of Nats.
“Yet another ATC system failure has resulted in the closure of UK airspace, meaning thousands of passengers’ travel plans have been disrupted.
“It is clear that no lessons have been learnt since the August 2023 Nats system outage, and passengers continue to suffer as a result of Martin Rolfe’s incompetence.”
More than 700,000 passengers suffered disruption when flights were grounded at UK airports on August 28 2023 when Nats suffered a technical glitch while processing a flight plan.
Mr McMahon continued: “If Nats CEO Martin Rolfe fails to resign on the back of this latest Nats system outage that has disrupted thousands of passengers yet again, then UK transport minister Heidi Alexander must act without delay to remove Martin Rolfe and deliver urgent reform of Nats’ shambolic ATC service, so that airlines and passengers are no longer forced to endure these preventable delays caused by persistent Nats failures.”
The Department for Transport (DfT) noted that the Transport Secretary does not have any direct control over Nats and has no powers on staffing decisions.
Nats has been contacted for comment.
The issue on Wednesday left many aircraft and flight crew out of position.
While it was ongoing, British Airways (BA) said the problem was “affecting the vast majority of our flights”, while Birmingham airport said “departing flights from many UK airports have been suspended”.
Several flights scheduled to arrive at UK airports were forced to conduct holding patterns or divert elsewhere.
In an update, BA said that the number of its inbound and outbound flights at Heathrow is restricted to a total of 32 per hour until 7.15pm before the flow rate returns to the usual level of 45 per hour.
Consumer organisation Which? advised that passengers who have suffered delays or cancellations could have rights to food or a hotel stay.
“If your flight is cancelled or delayed, you’re unlikely to be owed compensation by the airline as the technical issue is considered an ‘extraordinary circumstance’ and out of the airline’s control,” its deputy editor Naomi Leach said.
“However, you do have a right to food or a hotel stay depending on the length of the delay but be sure you keep the receipts as you will need to claim this back from the airline.”
The “technical issue” responsible for disruption was at Nats’ control centre in Swanwick, Hampshire, according to the company.
Transport Secretary Heidi Alexander said continued disruption was expected following the restoration of Nats’ systems and urged passengers to check with individual airports for advice.
A DfT spokesperson said: “We are working closely with Nats to understand the cause of the technical issue and the implications for the resilience systems in place.”
The Liberal Democrats called for a full investigation into the glitch.
The party’s leader Sir Ed Davey said: “It is utterly unacceptable that after a major disruption just two years ago, air traffic control has once again been hit by a technical fault.
“With thousands of families preparing to go on a well-earned break, this just isn’t good enough.
“The Government should launch an urgent investigation to ensure the system is fit for purpose, including ruling out hostile action as a cause.
“The public deserve to have full confidence in such a vital piece of national infrastructure.”
An expert said it is understood the software prioritises safety over keeping airspace open.
Junade Ali, a fellow at the Institution of Engineering and Technology, said: “Nats has previously thoroughly investigated such incidents and implemented suitable measures.
“From prior incident reports, the software is understood to not compromise safety at the expense of keeping airspace open.
“This is the right approach as, whilst keeping airspace open is important, the public risk appetite demands a high standard of safety when it comes to air travel.”
